THE EAR OF MAN. 



205 



tion of the auditory capsule forwards and outwards 

 (Fig. 10, d). 



Fig. 9. — The head of the 



embryo smooth Dog-fish 

 (^Galeus cajiis), seen from 

 the left side. Figure drawn 

 from nature, magnified 

 about 20 times. The 

 flask-shaped auditory vesi- 

 cle is shown prominently 

 placed above the gill 

 region. Letters as in the 

 preceding figure. 



a.v Auditory flask. 



e Eye. 



y Fore-brain. 



£ Gill region. 



h Hind-brain. 



m Mid-brain. 



n Nose. 



Fig. 10. — The head of an older Shark 

 of the same species, viewed from the 

 left side. The figure, which was 

 drawn from the living fish, shows 

 the internal ear well advanced in its 

 development. The rudiments of the 

 semicircular canals and lagena are 

 seen pushing out fcom the auditory 

 sack (respectively the utriculo-sac- 

 culus, which has sunk far below the 

 surface, with which it is, however, 

 still connected by its sickle-shaped 

 ductus endolymphaticus). 



During this lengthening of the neck of the flask, 

 which becomes the surface canal of the adult ear, the 

 body of the flask is much changed in shape. 



First of all, it becomes compressed laterally, and is 



