633 



The papilla lagenae lies anteriorly to the ridge, and posterior to this 

 is the papilla basilaris lying on the basilar membrane. Even the duct 

 connecting sacculus and cochlea shows indications of a double origin. 

 A comparison of series of horizontal sections through the pars inferior 

 of Rana fusca and Lacerta agilis respectively, first convinced 

 me of the homology of the parts of the cochlea in the two groups, 

 as far as the results of my own observations were concerned. The 

 chief differences are due to the fusion of the lagena and pars basilaris, 

 to the elongation of the connecting canal, and to the forward and 

 downward growth of the cochlear sac. The lagena is still anterior to 

 the pars basilaris, and the sacculocochlear duct opens near the posterior 

 medial border of the sacculus. The papilla basilaris becomes in the 

 Reptiles of as much importance as the papilla lagenae. In some forms 

 of the Lacertilia it already shows signs of obtaining the preponderance 

 it possesses in the Crocodilia, in Birds, and in Mammals. 



I give here a diagrams illustrating the relationships of the parts 

 in the two groups, Amphibia and Reptilia. It must be understood 

 that it is only by considerable distortion that the parts can be repre- 

 sented in one plane, and it seemed best to show an imaginary hori- 

 zontal section of the pars inferior, although even in this case it is 

 necessary to represent the parts of the cochlea as lying in the same 

 horizontal plane as the sacculus. This affects the accuracy of the dia- 

 gram more in the Reptilia than in the Amphibia, since in the former 

 the cochlea lies mainly ventral to the sacculus. 



Anterior 



Posterior 



S ' 



Pb 



Ms- 



Pl Ppb 



Fig. 2a. 



- Pb 



Fig. 2b. 



Fig. 2. a represents tbe condition in the Anura, b in the Peptilia (and Aves). 

 S sacculus, Ms macula sacculi, L lagena, PI papilla lagenae, Pb pars basilaris (with the 

 ''Knorpelrahmen"), Ppb papilla basilaris. (The outer wall of the sacculus faces upwards 

 in both diagrams.) 



Having seen that Dr. Alexander's view is based on a mis- 

 conception, and that there is no place for his new homology, it may 

 still be interesting to inquire how he would have proposed to explain 

 the origin of a completely new sensory area in the apical (anterior) 



