Proceedings of the Association of American Anatomists XV 



The cornea fails to develop when the optic vesicle is entirely removed. 

 Over the regenerated eye with lenses, a cornea develops normally except 

 for size, which is small to correspond to the small regenerated eyes. If 

 the optic cnp is torn out after the lens has separated from the skin, a 

 small area of clear epithelium will develop immediately over the undis- 

 turbed lens. Such clearing for the cornea will also develop over an 

 optic cup from which the lens has been extracted, but not in all cases. 



The vitreous humor develops only when both lens and optic cup are 

 present and in about their normal relations. 



We have here one tissue influencing another during the course of 

 development, and from this a new structure, the lens, arises. It seems 

 likely that there is a definite chemical reaction between certain substances 

 of the optic vesicle and certain substances of the ectoderm cells, which 

 results in the formation of new substances within the lens cells, and that 

 these substances give to the lens its peculiar characters and mode of 

 development. 



THE HEAD CAVITIES OF CERATODUS FORSTERI. By E. H. Gregoby. 

 Department of Anatomy, University of Pennsylvania. 



(Eead by title.) 



THE DEVELOPMENT OF THE LUNG OF CHRYSEMYS PICTA. By Wil- 

 liam S. Miller. University of Wisconsin. 

 If the lung of an adult C. picta be blown up, dried and cut open 

 longitudinally, it will be seen that seven distinct compartments, which 

 for convenience we will call air sacs, can be recognized; four of these 

 air sacs are larger than the other three. The three smaller air sacs are 

 situated on the mesial side of the lung between the first and fourth, 

 which occupy the cephalic and caudal ends of the lung. It will further- 

 more be seen that as we pass from the anterior to the posterior end of 

 the lung the air sacs become less and less complicated in structure. 



The same holds true for the lung in its development ; the more anterior 

 the air sac is situated the more complicated is its structure. The fourth, 

 or caudal air sac, although it can be recognized earlier than the fifth, 

 sixth and seventh, is much simpler in structure if studied in its entirety. 

 In the youngest embryo I have studied, the two primary lung buds 

 had already been formed as hollow outgrowths from the embryonic 

 bronchi ; these form the first or most anterior air sac. From the caudal 

 end of this enlargement a bud arises, which gradually grows caudad and 

 forms a nearly straight tube which presents successive enlargements that 

 ultimately develop into the second, third and fourth air sacs. 



