No. I.] THE VERTEBRATE EAR. 235. 



zu denken, an deren centrales Ende eine von einer Ganglienzelle 

 ausgehende Nervenfaser trate, die dann Entweder wie mir am 

 wahrscheinlichsten durch das Innere der Zelle, oder iiber die 

 oberflaclie derselben bis an die Basis des Haares oder der Har- 

 chen, vielleicht unter Theilung verliefe und hier mit einem 

 leicht veranderlichen Korperchen ende." With this as a basis 

 he passes on to a survey of the auditory organs of the main 

 divisions of the animal kingdom. It is unnecessary to follow- 

 further in this direction, for it is not possible at the present 

 time — much less so than when Hasse wrote — to homologize 

 the various so-called auditory organs of the invertebrates even 

 among themselves, and as the evidence accumulates we are 

 carried further and further away from the conception of a 

 genetic relationship of the vertebrate to the invertebrate audi- 

 tory organs of any group. Hasse's basis for the origin of the 

 auditory organs of all animals, — i.e. the hair-bearing nerve-end 

 cell is doubtless true, — but the same may be said of all sense 

 organs, and it is most probable now that the auditory function 

 as such was not assumed or acquired until after such sensory 

 cells became aggregated into groups or sense organs proper. 



I think that the views here briefly outlined, while certainly 

 not to be considered final or as all of them completely demon- 

 strated, may, nevertheless, serve to point out to us the salient 

 features of the future mammalian ear, since they are not with- 

 out an extensive morphological foundation. 



From the beginning the vertebrate auditory organ as a single 

 one (or a pair of) canal organs through modifications which it 

 (they) have suffered in the descent of the phylum, the canal 

 organ has been gradually losing ground and has been more and 

 more replaced by modified descendants, the most complicated 

 and peculiarly modified of which is the chain of transformed 

 organs known as the organ of Corti among the Mammalia, which 

 has descended from the papilla basilaris of the lower vertebrate 

 forms. 



The organ thus modified is typical, I think, of the future ear, 

 which will not retain much else than the cochlea. The semi- 

 circular canals will disappear, the maculae sacculi and utriculi 

 will gradually atrophy and their chambers become much modi- 

 fied or entirely aborted. 



The typical mode of disappearance of these organs is, I think, 



