354 



AVERS. 



lagenar group are represented as separated from each other by an interval, whereas 

 the actual relation in nature is much more intimate. 



ca., anterior canal. 



cp., posterior canal. 



ch., external canal. 



cab., abortive canal. 



u. utriculus. 



rec.utric, recessus utriculi. 



rec.sac, recessus sacculi. 



d., ductus endolymphaticus. 



s., sacculus. 



o.de., orifice of the same. 



Fig. 4. A surface view of the relations of the invaginated ear to the superficial 

 canal sense organs, in the ontogeny of the Spiny Dogfish, Acanthias vulgaris. 

 X 20. d.e., ear duct, o.de., mouth of same, opening through the skin into the ear 

 groove, aii.g. au.c, the line of canal sense organs, crossing the head and connect- 

 ing the two lateral systems, o.c. 



Fig. 5. Surface view of the nerve plate which enters the membrana basilaris. 

 From a preparation of the organ of Corti of the Dog, stained with alcohol carmine. 

 X 1065. The nerve fibres are shown crossing the space arched over by the pillars of 

 Corti, and reaching as far as the hair cells of the outer row. n.f., non-meduUated 

 nerve fibres, hb.p., line of the openings of the habenula perforata, v.s., spiral 

 vessel. 



Fig. 6. A series of the hair cells of the organ of Corti of the Virginia Opossum. 

 X 1065. The hairs are in large part removed, only one cell showing the basal rem- 

 nant of these structures. 



Fig. 7. The lower end of the basilar membrane and its bony framework, from 

 the adult human subject. X 3B0. n., the nerve fibres penetrating to the middle of 

 the basilar membrane, l.s.o., lamina spiralis ossea. 



