No. I.] 777^ VERTEBRATE EAR. 79 



The cochlear gangHon is inclosed in the bony plate, along the 

 inner border of the cochlear floor as in other mammals. 



The rods of Corti are placed on the basilar membrane at a 

 much sharper angle than they are in the higher Mammalia, in 

 consequence of which the canal of Corti is less broad than usual 

 in this class. This condition I consider to be more primitive 

 than the adult condition of the higher Mammalia, as the latter 

 forms pass through a stage identical with this, which occurs in 

 late embryonic life. 



Pritchard's deduction with reference to the homologies of 

 parts between the cochlear channels of Ornithorhynchus and 

 the higher mammals contains a grave error due, in the first 

 place, to his misconception of the true nature of the cochlear 

 tube especially, as well as of the so-called scalae, and secondly 

 to ignorance of the actual conditions existing in Birds. He 

 says {loc. cit. p. 278): that the lamina ossea of Ornithorhynchus 

 (and other mammals) corresponds to the avian quadrilateral 

 cartilage, and that the mammalian ligament um cochleae is rep- 

 resented in the Bird by the .triangular cartilage. Also that, 

 whereas the lower division or scala tympani of each corresponds, 

 the ductus cochleas of the Bird occupies the whole of the upper 

 division, and therefore corresponds to the scala vestibuli and 

 scala media (or ductus cochleae) of the mammal." 



That the cochlear tube of the avian ear possesses well-devel- 

 oped scalae tympani and vestibidi is such a well-published fact 

 that one is at a loss to understand how Professor Pritchard could 

 have overlooked it ; besides which, any transverse section of the 

 bird cochlea prepared with ordinary care would have prevented 

 the above blunder. 



The general rule which Hasse laid down that "wenn einmal 

 ein Theil mit einer macula oder crista acustica mit Nervenend- 

 apparaten des Hornerven differenzirt ist, dieser nicht verschwin- 

 det, sondern, namentlich wenn er die Schnecke angehort, in der 

 Wirbelthiere reihe immer mehr entwickelt," is no longer to be 

 considered as stating the usual course of events ; for of three 

 important exceptions to his rule the most important one affects 

 the strongest clause in the rule, viz. that concerning cochlear 

 organs. Unaccountable as it still is, the fact remains that the 

 largest and at one time most important cochlear organ does dis- 

 appear from the mammalian cochlea about the time of birth. 



