THE DEVELOPMENT OF DERMAL BONES IN THE SKULL OF A MIA CALVA.

In his study on the cranial development of Teleostomian fishes, the author had the opportunity of showing that the dermal bones in Amia calva, related to sensory canals, develop in close connection to the sensory organs in the canals. The author tried in the same paper to compare the rudiments of the canal bones in question with the canal bones in other recent fishes as well as in certain groups of extinct fishes in order to establish possible homologies between these bones. As far as the origin of the canal bones is concerned the author's observations seem to be accepted. Even the morphological value of the rudiments of the canal bones for comparative purposes has been accepted to a certain degree, especially by paleontologists, the objections advanced having chiefly concerned the interpretation of certain homologies. Lately the author had the opportunity of examining a series of embroynic stages of Amia Calva. This series is far more completed than the material on which he based his previous investigation.