1880.] On the Cochlea of the Ornithorhynchus platypus. 15B 



end of the duckbill's ductus cochleae ; this has never been found in 

 mammals, but is found in birds, reptiles, and amphibians. 



Comparison with the Bird. 



A brief description of the bird's cochlea, will be found in my paper, 

 in extenso ; in this abstract I propose only noting the similarities and 

 dissimilarities. 



The scalae tympani in each type of cochlea correspond. 



There is no scala vestibuli in the bird, the scala media (ductus) 

 occupying the whole of the upper division of the tube. 



The membrane of Reissner and stria vascularis is represented by 

 the tegumentum in the bird. 



The lamina ossea corresponds to the quadrilateral cartilage, and the 

 ligamentum cochleae to the triangular cartilage of the bird. 



There are no rods of Corti in the bird : the hair cells are more 

 numerous and their component hairs are united together into a spine, 



The nerve fibres pierce the quadrilateral cartilage by numerous 

 rows of holes, instead of one row, as in the duckbill and other mam- 

 mals. 



The lagena, with its macula acustica, is found both in the bird and 

 duckbill, but in the former is a direct continuation of the ductus, 

 whereas in the latter it is connected by means of a constricted tube. 

 Moreover, the ductus of the duckbill makes three-fourths of a turn, but 

 that of the bird is nearly straight. 



General Conclusions arrived at by the Research. 



Although the outer form of this monotreme's cochlea resembles that 

 of the bird in being nearly straight, yet its internal arrangement is 

 decidedly mammalian. 



The general acoustic apparatus of the duckbill's cochlea is not 

 nearly so extensive as that of "the ordinary mammal nor is its organ 

 of Corti so well developed. 



Lastly, the duckbill's cochlea possesses an addition, the lagena, 

 which is not found in any other mammal, but which is found in the 

 bird, reptile, and amphibian. Thus it presents a distinct link between 

 the cochlea of the higher mammals and that of the lower vertebrates. 



In conclusion, I desire to give my most hearty thanks to the many 

 Australian friends who, by their zeal in my cause, have provided me 

 with specimens of the ornithorhynchus in such a good state of 

 preservation as to allow of their microscopic preparation and 

 examination. 



