206 STRONG. [Vol. X. 



nervous systems. The development and specialization of these 

 structures have probably played an important part in the 

 changes leading to the organization of the vertebrate periph- 

 eral and central nervous systems. Furthermore, when we come 

 to compare the nervous systems of fishes and Urodela with the 

 higher vertebrates, without the general clue that these struc- 

 tures have disappeared, and the nerves supplying them likewise 

 either disappeared or metamorphosed, only false conclusions 

 are inevitable. 



Nor is the question one merely affecting the peripheral 

 nervous system, inasmuch as it affects likewise the central 

 terminations of this nerve supply and indirectly other portions 

 of the central nervous system in physiological connection 

 therewith. A number of changes in the higher centers will 

 probably be found to be connected with these transformations. 



As an instance of the effect of these changes upon the 

 central nervous system, aside from the medulla, it is possible, 

 I think, that the reduction of the cerebellum in Amphibia 

 may be correlated, to some extent, with the reduction in these 

 cutaneous organs. Its size in the higher forms would be, 

 perhaps, secondarily reacquired. 



As these changes in cutaneous organs are largely affected 

 by habitat, it is obvious that animals widely separated may, by 

 changing their habitat, undergo changes in their nervous 

 system quite similar in character. Here, again, we meet the 

 phenomenon of parallel changes in different forms, due to 

 similar conditions of environment, and, in such cases, of physi- 

 ological rather than morphological value. 



2. Relations of the Pre- and Postauditory Nerves. 



A peculiarity to which attention may be called here is the 

 position of the Auditory among the nerves. 



It is evident, from the description of the nerves of the 

 tadpole, that the pre- and postauditory nerves are not totally 

 different by any means ; yet, in general, there are marked 

 differences in the relative development of the different com- 

 ponents corresponding to the differences in the character of 



