226 AVERS. [Vol. VI. 



oped, and there may be still another. The one first mentioned 

 is given off from the utricular nerve, while the second branch- 

 let belongs to the saccular nerve. 



The papilla lagenas, which is so important in fishes, amphibia, 

 reptiles, and birds, has disappeared from mammalian anat- 

 omy — disappeared in the same sense that the macula neglecta 

 or crista abortiva has disappeared, by failing to appear in the 

 development as a discrete sense organ. The Monotremes, it is 

 true, are said to still retain the lagena, but they are hardly to 

 be accepted as typical mammals. The subject receives added 

 interest, however, from the fact of their still retaining the 

 organ beside a genuine reptilian (saurian) cochlear organ. I 

 think, by reviewing the matter in this light, that the views of 

 Hasse and Retzius, apparently antagonistic, are made harmo- 

 nious, and both are correct in the sense here indicated. 



The new auditory sense organ, which the brothers Sarasin 

 think to have discovered in the ear of IcJitJiyophis glutinosiis, 

 and which they propose to call the "macula fundi utriculi," is 

 in all probability no other than the macula neglecta. I may say 

 that Retzius's observations seem to me quite conclusive on this 

 point. The spot is evidently an offspring of the saccular macula 

 through the posterior canal organ, and so, in any case, belongs 

 to the posterior division of the auditory chamber. 



The proof is conclusive, I think, to show that Corti's organ 

 is not, as Retzius supposed, the homologue of the papilla basi- 

 laris of the Ichthyopsida and Sauropsida, but only a descendant 

 of this ancient organ. The differences of structure between 

 the embryonic and adult cochlear organ in the mammals that 

 have as yet been studied, are so great that we are justified in 

 speaking of Corti's organ as an entirely new organ, which arose 

 in the ear of the differentiating reptile in connection with those 

 changes which produced the profound modifications of other 

 organs of the body culminating in the mammalian type. The 

 growth of the organ has been such that a fragment of the coch- 

 lear organ invisible to the unaided eye is sufficient to enable us 

 to determine whether it was from a reptile, or a marsupial or 

 placental mammal. The changes that have occurred in this 

 organ in a microscopic way are then characteristic of what we 

 commonly speak of as changes in type of structure as applied 

 to gross anatomy, and they direct our attention to the fact that 



