Regulation in anuran embryos 



175 



By this time the larva showed well-developed eyes, mouth, 

 and nostrils, and was about 2 mm. long with a greatest breadth 

 of 1 mm. It did not die naturally, but was preserved, March 

 8th. At that time it seemed to be in good health with a fair 

 prospect of living on. t-'ections showed that internal gills and 

 the opercular cavity were well developed. The right tail had 

 relatively large dorsal and ventral f.ns in its posterior part, and 

 at its tip the left tail likewise had fins. The exposed yolk area 



Fig. 5 Transverse section of larva shown in figures 3 and 4, through anterior 

 end of yolk mass, arch, archenteron ; alt., tubes representing an alimentary canal 

 in process of formation; c, coelom; /, liver; Ibl, left blastopore lip; Im, left myo- 

 tome: Is, lymph sinus; ?tc, notochord; ///, neural tube; rhl, right blastopore lip; 

 r)n, right myotome; rpr., right pronephros; ya, exposed yolk area. X 67. 



measured in length about one-half the total length of the body. 

 Internally the yolk mass was found to occupy slightly moi-e than 

 this ratio. 



A study of the internal anatomy as made out in a series of 

 transverse sections gave the following facts: The brain, eyes, 

 auditory sacs, nostrils, mouth, pharynx, gills (internal), opercu- 

 lar cavity, and heart showed nothing obviously abnormal. But 

 in the trunk and tail region there were numerous results that 

 had followed from the failure of the blastopore to close. We 



