30 



SYDNEY EVANS JOHNSON 



eighth nerve of mterest m this connection. A. D. IMorrill, in 

 a xevy exact piece of work, found conditions in the auditory 

 epithelium of ^^lustehis which correspond ^'ery closely to the 

 conditions here described for the sensory epithelium of the lateral 

 canal, and from the morphological evidence now at hand it 

 seems fairly safe to conclude that the peripheral terminations of 

 the lateral and acoustic nerves are essentially alike, and that 

 these terminations are not in the nature of 'cups,' 'calyses,' or 



Sr^.Cl. 



rtr. 



Fhr. 



nin. 



17 



I*"ig. IG Longitudinal section of tlie lateral sensory column showing free nerve 

 terminations. Mustelus adult. Silver-pyridine tech. X 555. 

 ^ , Fig. 17 Longitudinal section of sensory epithelium showing fiber zone, free 

 terminations embracing bases of 'hair-cells,' and varicosities on fibrillae. Mus- 

 telus adult. Silver-pyridine tech. X 555. 



Fig. 18 'Hair-ceir and fibrillae bearing an unusually large varicosity. Mus- 

 telus adult. Silver-pyridine tech. X 555. 



complex anastomosing networks, but that the nerves terminate 

 in numerous delicate fibrillae which surround the bases of the 

 hair-cells to a gi-eater or less degree, and penetrate freely and 

 severally between the walls of the hair-cells. 



3. Develoipment of the sensory canals of Mustelus 



A complete series of Mustelus embryos could not be procured 

 and accordingly more detail of development will be brought out 

 in the following di\'ision of this paper dealing with Squalus 



