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Endocrine glands of the ironfish were studied light microscopically to elucidate the relationship between the races of the genus Carassius. The rostral pars distalis of the adenohypophysis consists mainly of acidophils corresponding to prolactin cells and lead-hematoxylin positive cells corresponding to corticotrophs (ACTH cells). The prolactin cells are obviously arranged in the form of follicles. The proximal pars distalis contains orangenophils (STH cells) and two types of basophils (TSH and GTH cells). In the pars intermedia, three types of cells are identified: periodic acid Schiff positive cells, lead-hematoxylin stainable cells and orangenophils containing PAS positive coarse granules. In addition, small agranular cells are seldom demonstrated in the entire adenohypophysis. A considerable amount of aldehyde fuchsin positive neurosecretory material is laden in the cells of the nucleus preopticus and in the pars nervosa. The nucleus lateralis tuberis is composed of three portions: pars anterior, pars posterior, and pars lateralis. The thyroid follicles found in the pharyngeal region and head kidney show a mild state of activity. The interrenal cells intermingled with the chromaffin cells have a considerable amount of eosinophil cytoplasm. Judging from the gonadal condition, the breeding season of the ironfish may extend to the end of July.

The adenohypophysis of the threespine stickleback, Gasterosteus aculeatus, was studied light-microscopically to determine and estimate the cell types and their function. For these purposes, the adult specimens obtained during the period from migration to spawning were examined. Further, the juveniles caught in the spawning bed were subjected artificially to sea water. The rostral pars distalis (RPD) consists mainly of two types of cells: dorsally shifted lead hematoxylin (PbH)-positive cells bordering the neurohypophysis correspond to corticotrophs, and antero-ventrally shifted acidophil cells are identified as prolactin cells. The latter undergo marked hypertrophy and active state just at the time of entering the river (February), while no detectable change was seen in the former throughout anadromous migration. The role of prolactin on the osmoregulation in freshwater environment is thus suggested. The proximal pars distalis (PPD) consists mainly of two cell types: the basophil cells in round shape are regarded as the gonadotrophs and the acidophil cells in ellipsoid shape are considered to be somatotrophs. The size of the gonadotrophs reaches the maximum at the time of spawning. A few AF-positive cells of elongate shape occur in the dorsal region and are identified as thyrotrophs. In the pars intermedia (PI), two types of cells are discernible: PAS-positive and PAS-negative cells. The latter attained their maximal size in the earliest time of anadromous migration.

A histogenetic study was done on the anterior pituitary of rats of both sexes progressing in age from birth to maturity. The results obtained were as follows:1. The parenchymatous cells of the rat anterior pituitary were composed essentially of chromophobe, acidophile and basophile cells. Two distinct cell types of basophils (delta- and beta-cells) could be distinguished by the application of the periodic acid-SCHIFF technique and GOMORI's aldehyde-fuchsin method.2. Chromophobes were generally small in size and contained fine filamentous material but no coarse secretion granules in the cytoplasm. Their cell boundaries were not as clearly defined as in the chromophils. The nuclei of chromophobes, round or oval in shape, contained relatively few chromatin particles and usually one or two acidophilic nucleoli. These cytological characteristics indicate that the chromophobes are in an undifferentiated state.3. Acidophils, though not as abundant as in adults, could already be identified by the presence of acidophilic granules in the cytoplasm immediately after birth. Acidophils were frequently observed to contain negative images of the Golgi apparatus in juxta-nuclear regions as cap-like figures and basophilic filamentous materials suggesting the presence of ribonucleic acid. As the animals approached maturity acidophils gradually became densely packed with cytoplasmic granules. On the whole there was a greater increase in the number of acidophils during growth and development of females than in males, therefore the number of acidophils in adult females exceeded that in males.4. Beta-cells characterized by the presence of cytoplasmic granules which react positively with the PAS reagent and aldehyde-fuchsin showed well-defined but irregularly shaped cell boundaries. These cells could be recognized from the earliest post-natal period. Their cytoplasmic granules gradually increased with age. In adult females most basophils were beta-cells, while in adult males delta-cells were predominant.5. Delta-cells were large in size, oval or round in shape, and had distinct cell boundaries. Their fine cytoplasmic granules which react positively with the PAS reagent and aldehyde-fuchsin were distributed throughout the cytoplasm except in the GOLGI area. Some of these cells were densely granulated especially in the peripheral zone of the cytoplasm. The negative image of the GOLGI apparatus of delta-cells was seen in the juxta-nuclear region as a clear, granule-free, circular area with a red centrum by the PAS technique or a dark blue centrum by the azan stain modified by MARTINS. In adult males, delta-cells were frequently found in the ventral area of the anterior lobe and the upper region adjacent to RATHKE's residual cleft. In adult females, on the other hand, delta-cells which were smaller in size and less granulated than those of adult males were located in the central region of the anterior lobe. In addition, most basophils of adult females were not delta-cells, but beta-cells.6. During the earliest postnatal life, delta-cells were scarce in number, small in size and showed feeble stainability for various dyes. In males, they became numerous and more densely granulated towards maturity. On the other hand, in females, they attained the maximum number on the 30th day, and decreased rapidly thereafter.7. Between the 35th and 45th day a remarkable change took place in deltacells of the females. During this period degranulation of delta-cells was observed. In addition, the majority of degranulated delta-cells was small in size when compared with delta-cells of the previous stage and had pycnotic nuclei, although delta-cells of the 30-day old female were similar in cytological details to those of males at the same age.8. According to PURVES and GRIESBACH (1954, 1955) and SIPERSTEIN, NICHOLS. GRIESBACH and CHAIKOFF (1954), two specific types of delta-cells were distinguishable in the rat anterior pituitary.

The author, using 218 hamsters of both sexes of various ages ranging from birth to 160 days, made a study on the postnatal development of the parenchymatous cells of the anterior pituitary in the hamsters. The results obtained were as follows:1. The parenchymatous cells in the anterior lobe are consisted of chromophobes, acidophils and basophils (beta cells and delta cells). In these cells, the mitoses are most numerous in number at 2nd and 3rd day, and always found throughout life, although they are rare in adult. The amitoses are found rarely in young animals, but not at all in adult.2. Chromophobes are generally small cells and have fine filamentous cytoplasm. The outlines of the chromophobes are not so clearly defined as in the chromophils. The nuclei are round or oval, relatively chromatinpoor and contain, as a rule, 1-2 fuchsinophilic nucleoli. They are thought of undifferenciated cells.3. Acidophils are characterized by the presence of fuchsinophilic or orangeophilic granules in the cytoplasm. They are clearly outlined, and generally round or oval in shape, although often appear considerably elongated when lie at the capillary wall. The negative image of the GOLGI's apparatus, which is restricted as a cap to one side of the nucleus, appears more numerous in female than in male. The count of these cells in the anterior pituitary increases far more in female than in male. The number of the cells of the anterior pituitary in male adult, reveal about 30per cent of all parenchymatous cells, and in female about 50per cent.4. The cytoplasm of the basophils contains varying amount of granular material, which are stained by the periodic acid-SCHIFF reaction. These basophils are more numerous in male than in female. In male adult, the number of cells reveal about 50per cent, and in female about 30per cent of all parenchymatous cells.5. The irregularly shaped beta cells are delineated by a distinct cell boundary and contain coarse granules which are stained by the periodic acid-SCHIFF reaction as well as GOMORI's aldehyde-fuchsin method. Especially, some of them appear to envelop the acidophil or chromophobe. In female the most of the basophils are beta cells and are scattered generally throughout the anterior pituitary, while in male they lie scattered in central region, being less in number.6. The delta cells are large, oval or round, and have respectively a distinct cell boundary. The fine granules, which are positive to the periodic acid-SCHIFF reaction, but do not stain themselves with GOMORI's aldehyde-fuchsin, are distributed throughout the cytoplasm. A negative image of the GOLGI's apparatus is seen as a clear, granula-free ring which surrounds a red (periodic acid-SCHIFF reaction) or dark blue (MARTIN's modification) centrum. The delta cells in male, which abound in the ventral area and lie along the cleft opposite the pars intermedia, are generally larger than those of female distributing in the central region.7. Occasionally, the cytoplasm of the delta cell of the male, contains a vacuole.

With rat fetuses of the 8th to 20th day of gestation and with neonates and postnates of one to seven days of age, the cytogenesis of anterior pituitary cells was investigated light and electron microscopically. The activity of pituitary trophic hormones was evaluated in reference to the histological findings on the developing target organs.The anterior lobe of rat fetuses, outgrowing from Rathke's pouch on the 15th day of gestation, consists of a single kind of agranular primordial cell. From the 17th day of gestation, they begin to granulate and turn into ambiguous cells containing minute granules, whose developmental orientation is still unknown. From the 17th to 20th day of gestation, the growing granules suggest their transformation into undifferentiated basophils. During late pregnancy the cellular transformation proceeds exclusively along the basophil axis, and undifferentiated thyrotrophs gain β-granules, and the follicles of the thyroid show a gradual development throughout perinatal life. In the late embryonal life, gonadotrophs with their characteristic large granules develop considerably in males. As this is timed by a transitory increase of Leydig cells in the testis, a discharge of gonadotrophin at this period is suggested. The involution of some gonadotrophs after birth is concurrent with that of Leydig cells. The development of gonadotrophs is delayed in female fetuses. No gonadotrophs reappear throughout postnatal life in either sex.The development of acidophils is retarded to that of the cells along the basophil axis during embryonic life. The ambiguous cells developing along the acidophil axis are generally ellopsoid or elongated in shape, and begin to contain dense granules. After birth, the cellular transformation along the acidophil axis is activated.Within 5 days of age, numerous young acidophils full of α-granules are produced. On the other hand, the fetal adrenal cortex has been substituted by the permanent cortex by the postnatal third day. The activated acidophil axis thus seems to be related to ACTH secretion.Pituitary primordial cells in embryonal life are characterized by abundant rosettes and the absence of dense granules. From the late fetal period on, they decrease in number, having been transformed into granulated cells. Some primordial cells are retained without completing their defferentiation into the so-called chromophobes, while the target organs are still developing. Mitosis takes place frequently in primordial cells and ambiguous cells, but not in mature chromophils. The present findings support the theory of two developmental transformation axes of the anterior pituitary cells.

In order to elucidate the details of the hypophysis of the puffer, Fugu niphobles, histological and cytological studies were performed on specimens collected at rocky beaches and specimens kept experimentally in dilute sea water. This species is known well as a marine fish by having a peculiar spawning habit and ascending behavior toward the river. The neurohypophysial ramifications penetrate extensively into the entire adenohypophysis, especially into the pars distalis. The adenohypophysis is divisible into three portions: the rostral and proximal pars distalis, and pars intermedia. The rostral pars distalis consists mainly of three glandular cells. They are lead hematoxylin (PbH)-positive acidophil (A1 cell), aldehyde fuchsin (AF)-positive and periodic acid Schiff (PAS) reaction-positive basophil (B1 cell), and the small chromophobe (C cell) cells. The proximal pars distalis includes two cell types: the dorsally shifted orangenophil (A2 cell) and more ventrally shifted, AF- and PAS-positive polyhedral cell (B2 cell). There are two types of cells in the pars intermedia: they are larger, PbH-positive acidophil (I1 cell) and smaller, weak PAS-positive chromophobe (I2 cell) cells. Two other strange cell types are also encountered in the adenohypophysis of some of the senile individuals. The C cells of the fish kept in 1/6 dilute sea water exhibit a marked hypertrophy in comparison with those of the fish kept in normal sea water. Some of the A1 cells are also activated by dilute salinity.