No. I.] THE VERTEBRATE EAR. 185 



an important part in separating this patch from the rest. 

 Besides, I do not think that the time of speciahzation of the 

 sensory tracts of the ampullae is a safe guide to the relative 

 times of evolution of the canals, as there is no rule of develop- 

 ment common to all three. If the ampullae were actually homol- 

 ogous structures, and their development had not been interfered 

 with, they would form in the same way; but as they do not do 

 so, it is safer to assume that the original course of development 

 has been modified, than that the ampullae are not homologous. 

 This would seem to show that the order of the evolution of 

 these epithelial patches has not been preserved." 



The sensory epithelium invaginated into the vesicle covers 

 the whole length of the floor, at the time of the appearance of 

 the utriculo-saccular septum, and passes up on to the inner wall. 

 It also laps over the anterior, lower, outer angle of the utriculus. 

 The sensory epithelium passes without sharp demarcation into 

 the remaining pavement epitheUum of the utriculus. As already 

 described, the utriculo-saccular septum divides this patch into 

 two, from the posterior of which the macula sacculi and the crista 

 acustica posterioris is budded off. Soon after this the macula 

 utriculi buds off a single small patch, which soon divides into 

 the cristae acusticae anterioris and horizontalis. The macula 

 sacculi lengthens, but for a long time remains continuous with 

 its bud, the cochlear organ. The lagena appears early after the 

 formation of the canals. The endolymphatic duct grows out 

 from the utriculo-saccular wall, and makes its way into the 

 cranial cavity, early establishing the relations characterizing it 

 in the adult. The manner of the division of the cochlear sense 

 organ into pars basilaris and lagena is not thoroughly under- 

 stood ; and I have not been able from my preparations to decide 

 whether it arises from the macula sacculi or from the papilla 

 lagenae. Villy erroneously includes the macula neglecta, i.e. 

 macula abortiva, in his list of cochlear sense organs : as I have 

 shown elsewhere, it really belongs to the sense organ of the 

 posterior ampulla. 



The Development of the Ear in Reptiles. 



Hoffmann (1889I) has worked out the development of the 

 parts of the ear in Lacerta viridis, and has confirmed Rathke's 



1 Bronn's Klassen u. Ordnutigen, VII, 3, 1SS9. 



