No. I.] THE VERTEBRATE EAR. 131 



to the anterior end of the macula acustica communis. From 

 the smaller, posterior ganglion there is given off an anterior 

 branch to the middle of the macula acustica communis, a poste- 

 rior branch to the region between the middle and posterior end 

 of the macula acustica communis, as well as to the crista acus- 

 tica ampullae posterioris. Both these branches are band-like 

 and relatively small. 



Of the nerve branches passing to the maculae, that of the 

 anterior ramus appears to be equivalent to the ramus recessus 

 utriculi, so that the anterior end of the macula communis would 

 be equivalent to the macula acustica recessus utricuH. The 

 anterior branch of the posterior ramus is the equivalent of 

 the ramulus sacculi, and its posterior branch, the ramulus 

 lagenae, so that the middle part of the macula communis equals 

 the macula acustica sacculi, while its posterior end equals the 

 papilla acustica lagenae. 



From the figures of the auditory nerve published by Ketel 

 (160, 1872) and Retzius (237, 1881), \hQ smaller posterior gan- 

 glion sends off two long, slender, fiat branches, of which the 

 anterior bifurcates and ends in the anterior part of the posterior 

 half, of the macula utriculo-sacculi. The posterior branch of 

 the posterior ramus bifurcates ; the anterior branch turns in- 

 ward and divides again and supplies the posterior portion of 

 the posterior half of the macula utriculo-sacculi. The largest 

 and most posterior branch runs direct to the posterior ampulla. 



The nerves pierce the membranous cover of the ear by a row 

 of holes running nearly in the long axis of the ear and below 

 its middle. The following table gives in parallel columns the 

 branches of the auditory nerve which I recognize in the Cyclo- 

 stome ear and those given by Retzius. I maintain that a split- 

 ting of the trunk of a nerve supplying the auditory organs 

 indicates the division of the sense organ supplied. 



Ayers. Retzius. 



1. ;', a, a,'\ 

 \ = I. r, a, a. 



2. r, e, J 



3- - . . , 



"^ ^ — ''' r, m,u. 



2 



5. r, in, u, "t _ 



4. ;-, r, t{, / 



5. ;-, /, = 3. r, s. 



6. r, s, = 4. r, I. 



7. r, ab, ~| 



' \=ie.r, a,p. 



8. r, a,p,\ ^ ' '^ 



