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A convenient, sensitive, and reliable assay for the conversion of radiolabeled sucrose to alcohol-insoluble dextran by the Streptococcus mutans dextransucrase has been developed.

The lactate dehydrogenase isoenzyme pattern of human dental pulps from deciduous teeth and normal and impacted permanent teeth were studied by means of cellulose acetate paper electrophoresis. A dominance of the LDH-3 and LDH-4 isoenzymes was observed. This result is further evidence for the presence of a prominent anaerobic metabolism in this tissue.

Human dentin and bovine skin collagens, partially hydrolyzed with acid, were compared by peptide mapping on thin-layer plates. The patterns, which showed 20 to 25 spots, were similar for the two types of collagen. No major differences in the structural characteristics of dentin and skin collagens can be predicted from these results.

Oxygen respiration was studied in bovine pulp slices exposed to temperatures of 50, 55, 80, and 100C. Results indicated that respiration is affected at 50C and destroyed at 55C. The significant but subnormal oxygen consumption measured in tissue heated at 80 and 100C is thought to be caused by autooxidation.

This study shows the buffering limitations of Krebs-Ringer-phosphate solution in the presence of acid production by dental pulp and indicates the need for appropriate selection of suspending fluid volume and tissue sample mass in reaction vessel loads.

Antimicrobial agents were used in the water coolant system in the high-speed dental drill during a series of tooth preparations on a model. Artificial saliva was applied to the dentition before the procedure began. For five minutes after cessation of drilling, the aerosols generated were collected on precipitation plates. Six agents reduced the bacterial counts to levels less than that recorded for water alone.

There is a growing need for high throughput diagnostic tools for early diagnosis and treatment monitoring of prostate cancer (PCa) in Africa. The role of cancer-testis antigens (CTAs) in PCa in men of African descent is poorly researched. Hence, we aimed to elucidate the role of 123 Tumour Associated Antigens (TAAs) using antigen microarray platform in blood samples (N = 67) from a South African PCa, Benign prostatic hyperplasia (BPH) and disease control (DC) cohort. Linear (fold-over-cutoff) and differential expression quantitation of autoantibody signal intensities were performed. Molecular signatures of candidate PCa antigen biomarkers were identified and analyzed for ethnic group variation. Potential cancer diagnostic and immunotherapeutic inferences were drawn. We identified a total of 41 potential diagnostic/therapeutic antigen biomarkers for PCa. By linear quantitation, four antigens, GAGE1, ROPN1, SPANXA1 and PRKCZ were found to have higher autoantibody titres in PCa serum as compared with BPH where MAGEB1 and PRKCZ were highly expressed. Also, p53 S15A and p53 S46A were found highly expressed in the disease control group. Statistical analysis by differential expression revealed twenty-four antigens as upregulated in PCa samples, while 11 were downregulated in comparison to BPH and DC (FDR = 0.01). FGFR2, COL6A1and CALM1 were verifiable biomarkers of PCa analysis using urinary shotgun proteomics. Functional pathway annotation of identified biomarkers revealed similar enrichment both at genomic and proteomic level and ethnic variations were observed. Cancer antigen arrays are emerging useful in potential diagnostic and immunotherapeutic antigen biomarker discovery.

SYNOPSIS IN INTERLINGUA ANALYSE DEL PORTION ORGANIC DE CALCULO DENTAL.—Specimens de composite e de separate calculos supra- e subgingival e de calculos ab dentaturas esseva decalcificate per le uso de 0,1 N de HCl e de un solution de 15 pro cento de tetraacetato ethylenediaminic a un pH de 7,0 a 7,5. Analyses chromatographic del hydrolysatos acide monstra que le mesme amino-acidos compone le portion proteinic del calculos supragingival como del calculos subgingival. Le aminoacidos trovate in mucina precipitate es simile a illos presente in calculos salivari. Le fraction carbohydratic del matrice organic del calculos esseva studiate per chromatographia a papiro. Galactosa, glucosa, mannosa, rhamnosa, e fucosa esseva detegite. In plus, il pare esser presente un hexosamina, un deoxy-sucro, e un acido sialic.

Four types of steel were tested, using dental instruments, for changes in hardness as a function of sterilization or disinfection. Steam autoclave, dry heat sterilization, and chemical disinfection were used. Knoop hardness was determined at intervals and data were statistically analyzed. Significant loss of hardness was observed in specific instances.

Two characteristics clearly distinguish between the dentitions of typical mammals and reptiles: generally the former are heterodont and diphyodont while the latter are homodont and polyphyodont. Superficially it might seem that by progressively reducing the number of replacement teeth in an evolutionary sequence of animals, it was a simple matter to arrive at a diphyodont mammalian descendant from a polyphyodont reptilian ancestor. But data on the sequences in which teeth are initiated in mammalian and reptilian embryos suggest that the process was more complex. In most reptilian embryos teeth are probably developed in sequences which pass through alternate positions from the back to the front of the jaw (Osborn, 1971). It is not easy to relate this sequence to that observed in mammalian embryos; for instance for the upper jaw of Eremnitalpa, Osborn (1970) gives the sequence it, i2, C, m4/M1/m3/i3/M2/M3/I1, 12, C, P3, P4/ 13 (in which the lower case represents deciduous teeth and the sequence is known only where bars separate teeth). Both heterodonty and a very limited number of replacement teeth also evolved in the postcanine dentitions of the gomphodont cynodonts and their descendants, the tritylodonts of the Triassic and Jurassic (Crompton, 1973). Although these animals finally become extinct in the middle Jurassic, it seems possible that the manner in which they evolved their limited numbers of replacement teeth from the ancestral polyphyodont condition might shed light on the evolution of diphyodonty in mammals. The earliest of the well-known gomphodont cynodonts with a markedly heterodont postcanine denition and a linited number of replacement teeth was Diademodon. The purpose of the present paper is to plot the sequence in which postcanine teeth were replaced in Diademodon and to compare this with tooth replacement in a polyphyodont reptilian dentition. If both have been correctly understood it should indirectly be possible to obtain some idea of the biological controls which regulate tooth replacement. And it can be safely assumed that by varying similar biological controls, mammalian diphyodonty could also have been evolved from polyphyodont dentitions. The pattern by which Diademodon, a lower Triassic gomphodont cynodont, replaced its postcanine teeth has recently been studied by Crompton (1963), Ziegler (1969) and Hopson (1971), and is also referred to by Crompton (1973). In view of the fact that no new data is provided in the present paper, it might seem unnecessarily contentious to propose a fourth solution to this problem within eight years. However, during the last decade almost all workers have, with varying degrees of success (e.g., DeMar, 1972) attempted to fit patterns of tooth replacement into the framework of a general model known as the Zahnreike theory. This theory, which was proposed by Edmund (1960, 1962), apparently links together tooth replacement patterns encountered throughout the vertebrate kingdom. My own studies, referred to above and later, have convinced me that the Zaknreike theory as a model describing the initiation of patterns of tooth replacement is untenable in the face of the phylogenetic and embryological evidence. I have concluded that the rate of tooth replacement is partly controlled at each tooth position.

This paper is based on a study of the variation and covariation of 18 morphological characters of the aphid, Pemphigus populi-transversus Riley, from 23 localities in eastern North America. The variation and covariation of these characters are separately studied within galls, among galls within localities, and among localities. By means of factor analysis, covariation is restated in terms of fewer dimensions (factors). The factors are compared at the different levels of variation. This paper continues an earlier study (Sokal, 1952) in which the author examined 21 characters of a single population of this gall-forming aphid from Ripley, Ohio. Of this local population, 28 galls containing four alate aphids each were studied. Since the alates within any one gall are isogenic and the different galls presumably represent different genotypes, the variance of the characters could be partitioned into a non-hereditary, intragall portion and an intergall portion which is assumed to be partly genetic and partly environmental in origin. Several characters, representing independent dimensions of intergall variation, were chosen by analysis of covariance. The purpose behind this procedure was the recognition of fewer than the original number of characters for a further study of intraspecific variation. Three problems emerged concerning the use of the characters chosen by the previous analysis. The first is the possibility, suggested by Clark's (1941) findings on Peromyscus, that the intergall correlations on which the former study is based might vary geographically, thus presenting a different pattern of significant characters in other areas. Average intergall correlations for many localities are therefore computed below. The second problem is whether some characters lacking intergall variance in the Ripley population might yet possess significant interlocality variance. As will be seen below, this proved to be the case for several meristic characters. Thirdly, and most important, are the characters representing genetic and environmental differences among galls necessarily the same as those describing genetic and environmental differences among localities? This study will show that there are real differences between interlocality and intergall factor patterns. As the study progressed a number of other objectives came into view, and assumed progressively increasing importance. The unusual hierarchic structure of the data at hand (isogenic alate aphids descended from a single stem mother, morphologically distinct but genetically identical, all contained within an individual gall; galls putatively representing different genotypes found within one locality; and finally localities presumed to differ genetically from each other) permitted a detailed and quantitative separation of sources of variation in this study. Since correlations can be computed at each of these levels of covariation, the differences between these correlation matrices and between the factors into which they were resolved eventually, provide a novel Part 2 of a study of variation in the aphid genus Pemphigus. Part 1 is Sokal (1952), part 3 is Sokal and Rinkel (1962). 2 Contribution No. 1125 from the Department of Entomology of The University of Kansas, Lawrence, Kansas.

In previous papers, experimental studies of the effectiveness of mimicry in two groups of North American butterflies have been described (Brower, 1958a & b). The present paper is an investigation of presumed mimicry in Danaus gilippus berenice (Cramer), model, and Limenitis archippus floridensis (Strecker), mimic, sometimes called the Queen and the Florida Viceroy, respectively. The mimetic relationship between these two butterflies first was noted by Scudder (1870), but D. g. berenice and L. a. floridensis have received less attention in the literature than their close relatives the model and mimic, Danaus plexippus (Linne), the Monarch, and Limenitis archippus archippus (Cramer), the Viceroy. Poulton (1909) has stated that there is no reason to suppose that the palatability of D. g. berenice to predators

In studying the evolutionary dynamics of polymorphisms in natural populations, most of the work in the past has concentrated on single genetic entities. The Work of Dobzhansky and his collaborators on the inversion sequences in the third chromosome of Drosophila pseudoobscura, the studies of Lamotte (1951) on shell color and banding in the snail Cepaea nemorallis, and those of Allison (1955) on abnormal hemoglobins in man are examples of genetic studies of polymorphisms controlled by alleles at a single locus, or else by blocks of genes which act in heredity as single loci. A new order of complexity is introduced when an attempt is made to study simultaneously two or more segregating systems in the same population because of the possibility, indeed the probability, that the evolutionary fates of the different polymorphic systems are not independent. Such will be the case if there is interaction between the different loci in the determination of the fitness of various genotypes. For example, the fitness of individuals of the genetic constitution AA may be greater than those with the constitution aa if at a second locus these individuals are, let us say, BB; but this fitness relationship may be reversed in the presence of bb at the second locus. In such cases the polymorphisms A,a and B,b are not independent in their fates in the population. Levitan (1955, 1958) in his studies of the inversion polymorphisms of Drosophila robusta has evidence of a small interaction of this sort and Cain and Sheppard (1954a, 1954b) have found such interactions for shell color and banding in Cepaea nemoralis. One of the most favorable materials for the study of these interactions and their evolutionary consequences is the Australian grasshopper, Moraba scurra. In an earlier paper (White, 1957) evidence was presented that the pericentric inversions, carried on two different chromosome pairs in this species, are not combined at random in the adult male individuals of certain natural populations. The deviations from random combination were regarded as proof of a genetic interaction between the two systems of cytological polymorphism, so far as their effects on viability are concerned. The significance of this interaction effect has been discussed and a hypothesis as to how it could have arisen has been suggested (White, 1958). The present paper has two purposes. First we shall present added data on the interaction effect from recent collections. The data published previously relate to six adult male samples collected in 1955 and 1956 at various localities in South Eastern Australia. Further data on two of these populations (at Wombat, New South Wales, and Royalla "B," Australian Capital Territory) were obtained in 1958 and 1959. Statistical analysis of the more recent data provides

For evident reasons, field studies of the population ecology of rare or sparsely distributed animals are almost nonexistent. Less easily explicable is the dearth of theoretical papers concerned with ecological factors which may come into play for sexually reproducing species at low density. Andrewartha and Birch (1954:333, 337-43) state the lack of studies of "underpopulation," noting possible reduction of the innate capacity for increase because of the failure to find mates. They give a detailed discussion of mate-finding in the sheep tick, Ixodes ricinus, based on work by Milne. They also discuss briefly (op. cit.: 695-697) possible effects, at population low, on genetic composition in a fluctuating population. Since their work, Philip (1957) has presented a study of population growth (or extinction) based on analysis using the probability of fertilization of females in a random model in combination with the logistic curve. Numerous papers presented by Wright (e.g., 1931, 1940, 1948) have noted the relative importance of random fluctuations in gene frequency (as opposed to changes in frequency due to natural selection) in populations with small effective population size. Summaries of the evolutionary significance of Wright's work can be found in Dobzhansky (1951) and in Li (1955). Pertinent to this study are Wright's conclusions as to the importance of populations of small effective size in evolution. Thus Wright (1931:157)

It has long been accepted by students of the genus Gossypium that the New World cottons (G. hirsutum L., G. barbadense L., and G. tomentosum Nutt.) are natural amphidiploids combining an A genome from a taxon of the Asiatic diploid group and a D genome from a taxon of the American diploid group (Skovsted, 1937). Beasley (1940b) and Harland (1940) provided confirming evidence on the origin of the New World type by synthesizing amphidiploids from A x D hybrids that were similar in morphology and cytogenetically compatible with the natural amphidiploids. More recent research on the general question of the origin of New World cottons has been directed toward pinpointing the taxa that were involved in the original hybrid and to the problem of "when" and "how" they were brought together so that hybridization could take place. These two questions form the basis of this paper, and they will be treated in turn. Triploid hybrids of New World (genome formula, AD) x Asiatic (A) and New World x American (D) show 13 II and 13 I at metaphase I (MI) of meiosis (this evidence supported Skovsted's hypothesis of amphidiploid origin). But since each of the two AD x A triploids and all of the seven possible AD x D triploids show essentially the same number of bivalents at MI, there is little basis here for identifying the parents of the New World amphidiploid. A method described by Stephens (1950) and used extensively in this laboratory (see review in Phillips, 1962) takes advantage of the segregation frequencies of marker genes in synthetic allohexaploids to discern interrelationships among the A, D, and AD taxa. A brief summary of the results of these studies (Gerstel, 1956; Gerstel and Phillips, 1957; Phillips and Gerstel, 1959; Phillips, 1962) appears in table 1. The relationships indicated in the table show that G. herbaceum and G. arboreum are very closely related to the taxon that contributed the A genome to New World cotton and that G. raimondii is rather closely related to the contributor of the D genome. The "gap" in this picture is the absence of the cross AD x D3 from table 1. Neither G. klotzschianum Andersson (D3-K) nor G. davidsonii Kellogg (D3-D), which some students of the genus consider to be conspecific, can be successfully hybridized with any of the New World species, and they will form vigorous hybrids with only two other species in the genus (G. anomnalum Wawra and Peyr. and G. longicalyx Hutchinson and Lee). There is thus no "direct" genetical or cytological method for assessing the relative chromosome homologies of D3 and DnW (D genome of New World cotton). However, by means of a bridging-species hybrid, the D3 and DnW genomes have been brought together in the same hybrid and their homologies compared by assessing chiasma frequency. By comparing chiasma frequency in this hybrid with that of a similar hybrid combining D5 and D,wy 'Contribution from the Crop Science Department, North Carolina Agricultural Experiment Station, Raleigh, N. C. Published with approval of the Director of Research as Paper No. 1509 of the Journal Series and with approval of the Crops Research Division, Agricultural Research Service, U.S.D.A.; supported in part by Project S-1 of the Research and Marketing Act of 1946. Aided by grant G-14203 of the National Science Foundation. 2 The genome nomenclature used in this paper follows Beasley (1940a and 1942) and Brown and Menzel (1950 and 1952).

It has been noted by several investigators (Dobzhansky 1944; Novitski 1946; Pavan 1946) that in some species of Drosophila, variability in chromosome structure is virtually restricted to one chromosome. At the same time, they note, the variable chromosome has a large number of inversions distributed throughout the species. This paper shall be addressed to the former observation, i.e., the concentration of inversions in one chromosome. One possible explanation is that the third chromosome is intrinsically more subject to breakage and rearrangement. This was tested by 1Hlelfer (1941) who irradiated D. pseitdoobscitra and demonstrated that the induced breaks and rearrangements occurred at random throughout the chromosonme complement. It is the purpose of this paper to present evidence for an alternative explanation for this non-random variation. It has been shown by Cooper, Zimmering, and Krivshenko (1955) that female D. melanogaster, heterozygous for two unlinked inversions, produce an appreciable proportion of inviable eggs; whereas females heterozygous for only one inversion are fully fertile, or virtually so. To explain this phenomenon, they suggest that in the females heterozygous for two unlinked inversions, there is the possibility of non-homologous pairing in meiosis, with unsymmetrical disjunction, and production of unbalanced gametes. If this situation were to hold for a natural population in which one chromosome had

In considering the origin of reproductive isolation, two theories, which are not mutually exclusive, have been advanced. Muller (1939) considers that reproductive isolation between two subspecies is just a consequence of their genetic divergence following selection in geographic isolation. In this way, as the divergence proceeds, genes that prevent free interbreeding will be incorporated into the genotypes of the two subspecies. On the other hand, Dobzhansky (1940) holds that divergence does not necessarily imply reproductive isolation. In becoming more adapted to their particular environments, each subspecies may diverge far enough so that hybrids between them are less well adapted to the available habitats than either parental subspecies. Natural selection then will work to build up a gene system for further reproductive isolation. The formation of ill-adapted hybrids is prevented, avoiding in this way a wastage of reproductive potential and food resources. Grant (1966) proposed that the process of selection for reproductive isolation be designated as the Wallace effect. In animals, there are some interesting experiments to test the origin of reproductive isolation. Koopman (1950) was able to demonstrate a marked intensification of the reproductive isolation between Drosophila pseudaoobscura and D. persimilis as a result of selection. The experiment was conducted below 16 C where little isolation between these two species prevails. Using stocks marked with different recessive genes, all hybrid offspring could be readily detected since they carried both dominant genes. All hybrid progenies were then eliminated in every generation, and in a few cycles of selection the isolation increased substantially. Using a similar technique, Knight et al. (1956) attempted to develop sexual isolation between two stocks within a species. Experiments were conducted with D. melanogaster for 33 to 38 generations and a partial sexual isolation was obtained. Experimental studies on the origin of reproductive isolation in plants are almost completely lacking. The present paper deals with the results obtained after selecting for intraspecific reproductive isolation between two varieties of maize. Different recessive marker genes were used in the two populations. Hybrids, resulting from heterogamic fertilization, were readily recognized and discarded in every generation. Since Zea mays L. has, perhaps, more genetic variability, it seems that except for the generation interval, maize is better material for such a study than is Drosophila. In fact, within the single species Zea mays L. over 250 races have been described as occurring in different areas of the Americas (Wellhausen et al., 1952, 1957; Hatheway, 1957; Roberts et al., 1957; Brieger et al., 1958; Brown, 1960; Grobman et al., 1961; Ramirez et al., 1961; Timothy et al., 1961, 1963). Some of these races are quite ancient, about 4000 years old, and some are of recent origin, being the result of hybridization among more ancient ones. Many kinds of variation in 1 Supported in part by grants from the Program in Agricultural Sciences of The Rockefeller Foundation. 2 This paper is part of the homage the Brazilian Society of Genetics pays to Prof. Th. Dobzhansky on his 70th birthday in acknowledgment of his effective role in developing genetics in Brazil.

The elaborate behavior patterns of wasps provide almost unlimited possibilities for comparative ethological studies. That few such studies have actually been made is in large part a consequence of the fact that the behavior of very few species has been described in adequate detail. The available descriptions are widely scattered in the literature and often fragmentary and poorly documented. Observers have often been unaware of the importance of certain components of the behavior, just as taxonomists often overlook structural details that later prove essential in classification. For this reason, there may be justification for studies which focus attention upon one particular facet of behavior and attempt to trace its modifications in various taxa. However preliminary, attempts to discern trends in the evolution of some aspects of behavior may provide direction for further studies. In an early and now classic paper, Ducke (1913) outlined the evolution of nest building in the Vespidae. Wheeler (1928) and others have considered the matter of the origin of sociality among wasps. Leclercq (1954) discussed the probable phylogeny of the Sphecidae as suggested by some aspects of structure and nesting behavior. The present paper is an attempt to outline the different ways in which wasps carry their prey to the nest and to draw certain conclusions regarding the probable phylogeny of prey-carrying mechanisms. Such mechanisms may or may not have obvious morphological components; in some cases, knowledge of the behavior may help explain the significance of structures which might otherwise be difficult to understand. Such an undertaking does not seem pre

In previous papers I have dealt with the taxonomy of the primarily tropical, loginhabiting genus Priochirus and with some aspects of the geographical distribution and ecology of species occurring in the Solomon Islands (Greenslade, 1971, 1972). The present paper gives an account of the evolutionary history of taxa within the genus. It depends on deriving evolutionary relationships of subgenera and groups of species from their morphology, a procedure that may be open to criticism, in particular for circularity of argument, if used alone. In this case, however, there is additional information which corroborates the results if it can be assumed, following Rensch (1959), that major evolutionary events are brought about by the same factors that are responsible for speciation. In this context major evolutionary events are the development of characters defining groups above the level of species; observations relating to speciation were made in the Solomon Islands. Here species' patterns of distribution were interpreted in terms of cyclic expansion and contraction of geographical range, accompanied by shifts of habitat (Greenslade, 1972). Taxonomic differentiation, which takes place concurrently, includes gross changes of structure. Together with data on the habitat ecology of species, these observations indicate both the direction of evolutionary change in morphology and the selective processes involved.

It seems reasonable to expect ecological theory to supply clear statements about the dominant forces which influence sequences of evolutionary change. This idea proceeds simply from the recognition that natural selection is identical with the interactions between organisms or populations and their secular environments. Such interactions determine probabilities of survival and reproduction as well as population size. This paper contains a theoretical treatment of the ecological and evolutionary exigencies imposed by a complex life cycle. For the purposes of this paper a complex life cycle is one which involves passage through two or more ecologically distinct phases. This means that there does not exist any overlap among the factors which limit abundance in each phase. Each phase thus has its own set of predator-prey, competitive, physical-environmental, and resource interactions. The following notation (adapted from Cole, 1954) will be convenient in designating important junctures in the life history of any species which exhibits two ecologically distinct life cycle phases

Observations have been going on in our laboratory for some time upon the distribution of fuso-spirochaete organisms in the body and on lesions in which they are found. As a result of these studies it seemed that inasmuch as one of the most important localities in which these organisms are often found normally is on and about the teeth, and since they are associated with many buccal lesions, it would be reasonable to expect them to occur often and possibly play an important r6le in alveolar lesions, especially the purulent and necrotic ones. We have already shown the significance of these bacteria in a variety of conditions including pulmonary gangrene, buccal lesions, genital lesions, etc. (3), and have called attention to their importance in determining the character of the lesion and to their association with pyogenic bacteria, particularly streptococci. In this paper we wish to emphasize this association of bacteria as a factor in determining the character and progress of lesions of this type in connection with alveolar abscesses. In the literature several papers have appeared on the bacteriology of alveolar abscesses. The first paper of importance is that by Gilmer and Moody (5), who found in a series of some forty cases the Streptococcus, viridans as the predominating organism in the exudate, and which they regard as the chief cause. They also state that "the anaerobic cultures which do contain streptococci are rarely pure. Some contain Bacillus fusiformis in varying numbers, a few of these tubes however have practically pure cultures of fusiform bacilli." They have emphasized (4) also the occurrence of putrefaction processes in alveolar abscesses in association with the activities of pyogenic cocci

In some families of plants and animals there is great uniformity of karyotype; in other families, sometimes even within a single genus, there is considerable variation. Where such variation exists, it is variation on an established theme, for karyotype like macromorphology arises as the result of various tendencies which preserve a somewhat unstable equilibrium within the organism. When it varies, it does not do so capriciously or arbitrarily. In groups where the usual taxonomic characters differ very slightly from species to species, chromosomal configuration may be a better guide to specific differences than the characters of external morphology. Within the genus Drosophila there is considerable variation of karyotype from species to species. The haploid number of chromosomes varies from three to six, and individual chromosomes may be rods, dots, V's or J's in varying sizes and proportions. Certain general configurations are found widely spread throughout the genus,; again, two species scarcely differing morphologically may have very distinct chromosomal complements. The several very similar species of the virilis group were first satisfactorily separated as a result of chromosomal analysis (Patterson, 1943). The guarani group consists of six species which on the basis of morphology are very closely related. They clearly belong to the subgenus Drosophila but are not closely related to any other known species of the genus. The present paper deals with the chromosomal configuration of these six species and the light which this chromosoinal analysis sheds on the interspecific relationships within the group. Another paper dealing with the general interspecific relationships aside from the chromosomal configurations is in preparation and will be published shortly. The six species of the guarani' group are the following: guarani' Dobzhansky and Pavan, guaru Dobzhansky and Pavan, guaramurnu Dobzhansky and Pavan (Dobzhansky and Pavan, 1943), griseolineata Duda (Duda, 1925), subbadia Patterson (Patterson, 1943), and guaraja, species nova, described below.

As a result of some two years' field work on the fauna of Lake Nyasa, and subsequent analysis of the information gained, a number of points relevant to the evolutionary phenomena shown by that fauna have emerged. Some of these have been mentioned in previous papers, particularly in one dealing with the ecology and evolution of some of the littoral fishes (Fryer, 1959), but several points, albeit disconnected, but none the less pertinent, remain to be presented. It is the purpose of the present paper to draw attention to these points.

It has been known for many years that interspecific hybridization within the genus Betula occurs more or less freely in nature. Woodworth (1929) states that at least 15 recognized hybrids occur in the genus, including Betula pumila x Betula lenta, Betula populifolia x Betula papyrifera, Betula verrucosa x Betula papyrifera, and others. Rosendahl (1916) also reported and analyzed hybridization within the genus, including a cross involving Betula papyrifera and Betula pumila var. glandulifera. In addition, Betula is known to be a polyploid genus (Woodworth, 1929). This paper' deals with the first instance in which hybridization has been reported involving Betula papyrifera and Betula occidentalis. Wherever two species likely to hybridize grow together, and conditions are more favorable to one than to the other, introgressive hybridization may occur. Anderson (1949) has described this phenomenon as a contamination of the germplasm of one species by the germplasm of the other. The species less favored by present conditions may gradually be absorbed by the other, and the external characteristics of the hybrid derivatives will be more and more those of the best preadapted species. In the fall of 1906, Mr. Darwin M. Andrews, a nurseryman, discovered a small grove of paper-barked birches on the northwest slope of Green Mountain, a high foothill immediately southwest of Boulder, Colorado. Dr. Aven Nelson, to whom Andrews had sent specimens of the birch for identification, published a note (Nelson, 1907) drawing attention to the Andrews collection. The somewhat nvunicrl character' of the nrecimpno, and the geographic isolation of this birch community led Nelson to believe that these plants might constitute a new species, distinct from Betula pap yrifera Marsh, the commori paper-barked tree of northern and eastern North America. However, because of the incompleteness of the specimens before him, and because of his inexperience with 'the population in the field, Nelson only tentatively named this birch "Betula andrewsii," which name was, of course, a nomen provisiorum and therefore not valid until its subsequent publication in Coulter and Nelson, New Manual of Botany of the Central Rocky Mountains (1909). Bertram T. Butler (1909), in his taxonomic revision of the paper birches, did not think there were sufficient grounds for separating Betula andrewsii from Betula papyrifera. Dr. Francis Potter Daniels (1911), in his Flora of Boulder, Colorado, and Vicinity, formally reduced Betula andrewsii to a trinomial, Betula papyrifera andrewsii (A. Nels.) Daniels. Daniels' reduction of Betula andrewsii to subspecific rank may have been a factor in a subsequent neglect of the problem. At least, recent authors of tree' manuals have not attempted to determine further the possible relationships of Betula andrewsii. The status of Betula andrewsii has remained unsettled to the present time. The herbarium material of this taxon consisted, until recently, of the type collection (a branch with yellowed leaves and fragmented aments, plus a strip of bark) collected in the fall of 1906, and a branch collected early the following year. This collection is in the Rocky Mountain Herbarium'of the University of Wyoming at Laramie. A photograph of the tree

The spatial variation of gene frequencies has been recorded in several polymorphic species, including Biston betularia (Kettlewell, 1958), Cepaea nemoralis (Lamotte, 1951, 1959; Cain and Sheppard, 1954), C. hortensis (Clarke, 1962), Littorina obtusata (Sacchi, 1961), Homo sapiens (Allison, 1955), Drosophila spp. (Dobzhansky, 1951), and Spaeroma serratum (Bocquet, Levi, and Teissier, 1951; Hoestlandt, various papers). In at least the first five species, there are indications of the reasons for the variation. In some species changes in gene frequencies have been recorded as well (see, for example, Sheppard, 1961, on Panaxia dominula; Dobzhansky, 1958; Clarke and Murray, 1962). The causes of spatial variation and changes in gene frequencies in natural populations are controversial, with more importance ascribed to selection (Cain and Sheppard, 1954; Fisher and Ford, 1947) or to random drift (Lamotte, 1959). As Wright (1948) has emphasized, however, these are not exclusive categories but may interact in certain circumstances. The purpose of this paper is to describe the genetics of the polymorphic isopod, Sphaeroma rugicauda Leach, and to consider some aspects of gene-frequency data from 46 British populations of the species which suggest that natural selection is responsible for differences between populations.

It is commonly assumed that the relatively small body size of recent amphibians is correlated with the important part played by cutaneous respiration in these animals. Findings providing information on the evolution of size in Amphibia are considered below. The weight of an animal increases as the cube of its linear dimensions, whereas the surface area of the skin increases only as the square of the body length. This results from the equation connecting the surface with the volume of similar bodies, which is S = kv2/3 where S = surface, v = volume, k = factor dependent on the shape of the body, lowest for the sphere and increasing with the complication of the external surface. The exponent %/3 is often expressed as a decimal fraction: 0.666. It is therefore to be expected that the larger the amphibian, the less efficient is its skin respiration It is also well known that in the majority of animals the increase in size is accompanied by a decrease in tissue metabolism, as measured by the ratio of metabolism to weight (Rubner, 1908; Zeuthen, 1953; Bertalanffy, 1957). An extensive survey of this relation was published recently by Hemmingsen (1960). This author was able to demonstrate that the best approximation to the values observed in measurements is obtained with the equation M = kmn where M is metabolism, m is the mass of the animal, and the value of the exponent n is 0.75 or 3/4. It was therefore demonstrated that the metabolism of many different organisms does not diminish at the same rate as their surface, but at a somewhat slower pace. Some facts collected during an extensive 4,fildv of the vx7iri11ari7.itinn nrld PtriictiirP of amphibian respiratory organs throw light on this problem. The detailed data were published before in several papers (J. Czopek, 1955a; J. Czopek, 1955b; G. Czopek and J. Czopek, 1955; Szarski, 1955; Strawin'ski, 1956; J. Czopek, 1958; G. Czopek and J. Czopek, 1959; J. Czopek, 1959a; J. Czopek, 1959b; J. Czopek, 1959c; Andrzejewski and Maciaszek, 1960; Bieniak and W4tka, 1962; J. Czopek, 1962a; J. Czopek, 1962b; Andrzejewski et al., 1962; G. Czopek et al., 1962). Data presented in these publications -were used in preparing figs. 1 to 3. Methods used for the accumulation of the data were quite simple: they consisted of injecting blood vessels with Prussian blue or India ink, of counting under a microscope the number of capillary meshes in a field of vision, and of calculating the total number of respiratory capillaries per unit of body mass. Detailed descriptions of these methods are to be found in J. Czopek's papers (1955a, 1962b). Amphibians use for respiration the skin, the mucous membrane of the mouth cavity, the gills, and the lungs. These organs will be discussed in this sequence.

Four species of Trillium occur in the western United States. Two of them, T. rivale and T. petiolatum, have relatively restricted areas of distribution and are not considered in this paper; the other two are found in all the Pacific States (Abrams, 1940; Gates, 1917). Trillium sessile3 is found from the Olympia Peninsula, Washington, to San Luis Obispo and Mariposa Counties, California, and is most frequent in the valleys of the Coast Ranges where. it is confined to the humid shade of deciduous woods. Trillium ovatum, on the other hand, is associated with coniferous forest (but not under pines) throughout the Coast Ranges from Vancouver Island to Santa Cruz Co., California and eastward across the Rocky Mountains to Montana. The purpose of this paper is to compare the pattern of chromosome differentiation in Trillium sessile and T. ovatum in relation to the size, history, and breeding structure of the populations.

Very similar species are of great interest to students of evolution because such species probably have evolved recently, making it likely that much of the evidence of their origin can be reconstructed. In very few instances of closely similar non-polyploid plant species is there evidence to suggest that one is the ancestor of another. A notable example is the cytological evidence for the origin of Crepis fuliginosa (n-= 3) from C. neglecta (n = 4) or its near ancestor (Tobgy, 1943). Similarly, Sherman (1946) showed that Crepis kotschyana (n = 4) has been derived from an ancestor like C. foetida (n 5). Another convincing example of an aneuploid species with a living diploid ancestor was described by Lewis and Roberts (1956) in their studies of Clarkia biloba (n= 8) and C. lingulata (n -9). These two species are so similar that they can only be distinguished by petal shape and chromosome number. Cytogenetic analysis showed that C. lingulata has an additional chromosome composed of parts of two chromosomes of the C. biloba genome. The presence of duplicated chromosome material in C. lingulata clearly establishes it as a derivative of C. biloba. Recently, Jackson (1962) described a case in Haplopappus that also suggests the origin of one diploid species from another. What was considered Haplopappus gracilis was found to consist of two extremely similar species, one with a chromosome number of n = 4, the other with n = 2. Cytological evidence indicates in this instance, as in Crepis, that aneuploid reduction is the most probable explanation for the difference in chromosome number, with the n = 2 species the derived one. The purpose of this paper is to present a unique example in Chaenactis (Compositae) in which the cytogenetical evidence indicates beyond reasonable doubt that an extant species of relatively mesic habitats, C. glabriuscula DC., has given rise independently to two similar desert species, C. fremontii Gray, and C. stevioides H. & A., by aneuploid reduction in chromosome number. Chaenactis comprises approximately 24 herbaceous species, all endemic to western North America. There are at least nine annual species, and four of these, C. glabriuscula, C. stevioides, C. fremontii, and C. xantiana form a closely related assemblage,2 judging from their similarity and frequent natural hybridization. The first three will be considered in detail in this paper. The yellow-flowered C. glabriuscula is the most variable, and some of its intergrading variants have been treated as separate species.3 Chaenactis stevioides and C. fremontii have white flowers, but are otherwise very similar morphologically to certain populations of C. glabriuscula. Despite their overall similarity, the gametic chromosome number of C. glabrius

Presently available research literature includes no less than a score of North American studies pertaining to the time and sequence of eruption of the primary or "'milk" teeth. For only about one-sixth of these studies is the medium of original report a dental periodical, the remaining five-sixths are in anthropological, biological, child development, medical (mainly pediatric) and psychological publications. It is a major objective of this paper to bring together these widely scattered reports and make their contents more readily accessible to members of the dental profession. A second major objective of the paper is that of presenting an epitome of research knowledge concerning the age and order of eruption of deciduous teeth in North American children. This, of course, presupposes a systematic and comprehensive integration of the materials from different studies. The two objectives determine the two parts of the paper: The first-colligation-is carried out under the caption "Presentation of Research Materials" and the second-synthesis-under the caption "Generalizations." There are incorporated in both parts the findings from two previously unpublished investigations.

The origin of a higher category involves a structural and functional transition from one adaptive zone to another. During the transition, the character complexes undergoing change do not necessarily evolve at the same rate or at the same time. The evidence for this conclusion is mostly provided by a few examples in the vertebrate fossil record. Actually, the great majority of families, orders and classes of invertebrates, and most higher categories of vertebrates, possess all or most of their distinguishing characters at the time of their first known appearance in the record. Transitional forms frequently combine primitive and advanced characters in such a way that allocation of these forms to an ancestral or a descendent category becomes more or less arbitrary. De Beer (1954), in a recent discussion of the nature of the transition phase, points out that the shift from one major group to another involves animals that possess a mosaic of nearly static ancestral and evolving descendent characters. Mosaic evolution, as he terms it, is thus characteristic of the transition phase. An important consideration in the concept of mosaic evolution is the manner in which morphologic change occurs. De Beer (ibid., p. 169) states that "owing to the genetic make-up and the internal conditions of development in an organism, there may be only a limited number of changes possible, and it is legitimate to think that changes restricted to single organ-systems are more likely to have occurred than progressive changes affecting the entire organism. It is further probahie that chrnngees restricted to single organ-systems at a time were more viable and less likely to succumb to selection." The purpose of this paper is to consider some aspects of mosaic evolution in a group of extinct ray-finned fishes called the subholosteans by a study of associations between pairs of generic characters tested by the chi square method. This approach is in a sense tentative and exploratory for reasons which will be evident later. Other groups of fossil organisms showing greater taxonomic diversification, particularly among the invertebrates, should permit more thorough statistical treatment and hence more positive conclusions in relation to association. The subholosteans show varying degrees of advancement, from a primitive level, represented by the paleoniscoid fishes, toward a higher level, exemplified by the holostean fishes. The subholosteans, as well as the examples of mosaic evolution cited by De Beer, indicate that the transition changes do not involve single organ-systems but rather functionally integrated structural complexes that may involve components of a number of organ systems (as De Beer implies elsewhere in his paper). For instance, modifications in the feeding mechanism nearly always include changes in the skull, in the jaw musculature, and to some extent in the nerve supply and the circulation. There is also good reason for believing that changes may occur in different parts of the body more or less simultaneously but independently of each other. All alterations must, of course, be integrated in respect to the entire organism, but this does not necessarily involve close functional interdependence of all the complexes undergoing change at any particular time.

The paper studies 60 Class II, Division 2 malocclusions, from lateral skull radiographs taken before treatment and at least 1 year after the end of retention. In the first part of the paper the nature of the malocclusion is analysed. It usually exhibits a Class II skeletal pattern, and while this is on average milder than for Class II, Division I, there is a marked variation between individuals. Other factors are a high inter-incisal angle, a high lip-line, and in some cases a small lower facial height. The upper and lower facial heights, on the other hand, are not appreciably greater than normal. The results of treatment are then analysed. Successful overbite reduction would seem to be associated with a reduction in inter-incisal angle and a relative lowering of the lower lip-line. Growth appears to be important in achieving overbite reduction. It is suggested that favourable rotation of the mandible may be a factor in overbite reduction in some cases, and this would repay further study. Finally attention is turned to the effect of incisor proclination. This was usually more successful in the lower jaw, but again there was wide individual variation.

In the foregoing paper of this series (Fukuda et al., 1960), migrations among natural populations of Trillium kamtschaticum across the Ishikari Depression, a narrow depressed area connecting the southern part of Hokkaido with the central part, were investigated. The present paper deals with migrations that have taken place in the north-eastern region (Kitami Province) of Hokkaido, where the northern population group (North) of this plant borders on the eastern one (East). The front of the contact of these two groups ranges from the seashore of Okhotsk, passing through the interior of Kitami Province, to the central part of Hokkaido, where volcanoes of central Hokkaido divide the two groups (fig. 2 in Fukuda et al., 1960 and fig. I in the present paper). Seven populations, Ke, Op, Sk, Ab-1, Ab-2, Mb and Tp, distribtuted in the coastland facing the sea of Okhotsk and two, B1z and Ot, from the coastland of Nemuro Province, were chosen for examination. Also, four populations Eg, Ok, An and Kt, were taken from the interior of Kitami Province (fig. 1 ). The migrations were examined by making analyses of chromosome composition of these populations.

When any one of the three beetles Rhizopertha dominica Fab., the small strain and the large of Calandra ory2ae L., was allowed to increase in numbers in a limited space in which the amount of food was kept constant, the maximum numbers which the populations attained were correlated with the innate capacity for increase (or the intrinsic rate of increase r) (Birch, 1953b). In this paper we shall examine whether there is a relationship between the numbers of these beetles and their innate capacity for increase when two species occur together in the one population. The experimental models which were set up are similar to those described in an earlier paper (Birch, 1953b) in which single species multiplied in amounts of grain which w7ere kept constant, except that in the present experiments each tube of grain contained two species; an adult male and female of each species were placed in each tube at the beginning. Combinations of temperature, moisture and food were chosen so that in some experiments one species had a higher innate capacity for increase than the other whilst in other experiments this same species had a lower innate capacity for increase than the other. The appropriate information for planning the experiments in this way was obtained from a previous paper (Birch, 195,3a). This latter aspect constitutes the novel feature of these experiments. Other workers have done experiments in which

Recently estimates have been published for the dates of divergence of various primate lineages, including man's, based primarily on the comparative immunology of serum albumin (Sarich and Wilson, 1967a, 1967b; Sarich, 1968). These dates differ rather radically from those derived from a study of the primate fossil record, and it is the purpose of this paper to consider the paleontological and biochemical data bearing on this problem and to evaluate the respective methods. We discuss the fossil evidence in the first part of this paper, the biochemical data in the second.

In the course of research on the embryology of the reptilian nose, I concluded that the structure and development of the nasal cavities in various recent tetrapods might give some clews to the phylogeny of the major groups of reptiles. The detailed results of this research are being published elsewhere (Parsons, in press), but it seems advisable to consider the major phylogenetic implications separately, without burying them in a mass of descriptive data; such is the aim of this paper. The division of the class Reptilia into major subgroups and the relationships between such subgroups have long been subjects of debate in the literature. On the basis of the anatomy of the heart and aortic arches, Goodrich (1916) proposed dividing the reptiles into the sauropsids, comprised of all the living orders of reptiles and their fossil relatives including the ancestors of birds, and the theropsids, those groups of extinct reptiles which are related to the ancestry of mammals. His views have been widely accepted by many workers, especially Watson (1951-1957) who has utilized the anatomy of the middle ear as further evidence for the separation of sauropsid and theropsid reptiles. However other authors have been impressed with the differences between turtles and all other recent groups. The most important paper stressing these differences, especially those in the skull, is that of Olson (1947), who divides the reptiles into the Parareptilia (turtles and fossil relatives) and the Eureptilia (all other reptiles, including the other recent reptilian orders and the ancestors of both birds and mammals). Obviously in any subj ect of disagreement such as this, more evidence is needed. Nasal anatomy appears to offer some assistance, and is therefore of considerable interest. Although detailed anatomical descriptions are beyond the scope of this paper, a brief outline of the major features of each group is included before the more detailed consideration of the phylogenetic implications. The following section is essentially a rather extensive footnote or appendix presenting a summary of the data on which the remainder of this paper is based. More complete anatomical descriptions and many references to the literature may be found in the works of Matthes (1934) and Parsons (in press). Major papers on the olfactory bulbs and neural connections of the nose include those of Zuckerkandl (1910), Herrick (1921), and Crosby and Humphrey (1939). All the observations summarized below are taken from these works or works cited in them. I am indebted to Drs. Ernest E. Williams and Alfred S. Romer of Harvard University for their many helpful suggestions and comments concerning this subject, and to Drs. Williams and Ernst Mayr for kindly reading the manuscript for me. Finally my thanks are due to Mrs. Thomas S. Parsons for assistance in the preparation of the manuscript and, especially, the illustrations.