THE CHONDROCRANIUM IN THE ICHTHYOPSIDA. 115 



in the Anura we find a much more complicated condition. 

 The fenestra ovalis passes through important changes of 

 form and the stapes comes into connection with a tym- 

 panic annulus. But if the tympanic annulus was "orig- 

 inally a postero-superior leaf cut off from the mandibular 

 suspensorium," as stated by Parker and Bettany ('77), 

 the fundamental similarity of the conditions in the two 

 groups is apparent. In connection with this point Gaupp 

 says, "Der vom Quadratum losgeloste knorpelige Annulus 

 tympanicus scheint eine dem Anuren allein zukommende 

 Bildung zu sein." Here, as with the Urodela, the nasal 

 capsule offers little that is of classificatory value. 



The chief" points of difference between the chondrocra- 

 nium in the two groups may be tabulated as follows : 



Urodela. Anura. 



1. Both broad and narrow types. 1. Generally, if notalways, broad. 



2. Pterygoid free in front (ex- 2. Pterygoid attached to ethmoid 



cept in Ranodon). plate. 



3. Basi- and supra-cranial fonta- 3. Basi- and supra-cranial fonta- 



nelles large. nelles smaller. 



4. No metamorphosis. 4. Very striking metamorphosis. 



6. Auditory apparatus compara- 5. Auditory apparatus, including 

 tively simple. the tympanic annulus, com- 



plex. 



ICHTHYOPHIS GLUTIN08US. 



First stage. — (Figs. 22 and 23). — The specimen from 

 which the model for this stage was made was a young 

 embryo still spirally coiled within its membranes. While 

 in some places, more particularly toward the anterior end 

 of the head, the tissue modelled is not true cartilage, the 

 differentiation of all the parts is sufficient to cause little 

 difficulty in distinguishing them. 



