No. I.] 



THE VERTEBRATE EAR. 



139 



ized fibres from the sense organs of this now highly modified 

 canal complex. TJiis sajne process occurs m the ontogeny of the 

 auditory organ of the Elasniobi'ancJis as the normal one. 



Thus we see that the conditions exist to-day in such forms 

 as Teleosts and Ganoids, from which a second set of ear organs 

 might readily be produced with a repetition of all the essential 

 processes now occurring in the more ancestral Elasmobranchs, 

 including the nerve supply, and the relative position of the 

 organ with respect to the VII and IX nerves. Showing thus 

 how it might again take place, aids us in comprehending how 

 it has taken place in time past, and clears up many obscure 

 points in the ontogenetic processes of existing Elasmobranchs, 

 in so far as the auditory organ is concerned. 



Goronowitsch found that both the dorsal branch of the VII 

 and the anterior (dorsal) branch of the IX arose in common 

 from the so-called dorso-lateral tract of Acipenser, which gives 

 rise from its ventral portion to the auditory nerve, although a 

 portion of its fibres arise from the posterior longitudinal. tract. 



He says (p. 511, loc. cit.) : "Der Acusticus wird durch Fasern 

 eines und desselben Charakters gebildet. Sie sind um etwas 

 feiner als die Fasern des N. 1. lateralis und betrachtlich dicker 

 als die Fasern der dorsalen Wurzel des Facialis und des Tri- 

 geminus II." The nuclear connection Goronowitsch describes 



Cut 12. — The branches of the auditory nerve of Ostracion cormitus and their 



distribution: cr.a., cr.p., cr.e., the nerves of the three ampullar sense organs, ni.s., 



the nerve supply of the sacculus. m.ti., the nerve supply of the utriculus. ;'./., 

 the ramulus lagense. 



as follows : " Einen anderen Faserantheil bekommt der Nerv 

 aus der Zellgruppe Az, welche ventralwarts vom Facialis (Radix 



