2 'Journal of Comparative Neurology and Psychology. 



The siluroids, owing to the enormous number of taste buds 

 scattered over practically the whole of the body surface, seemed 

 the most favorable group for such a study and Ameiurus melas 

 in particular was selected on account of the very complete descrip- 

 tion of the distribution of the gustatory fibers which has been given 

 for this type by C. J. Herrick ('oi). 



Owing to the fact that all taste buds wherever located are inner- 

 vated by communis fibers and that those in the endoderm of the 

 pharynx appear in some forms before buds appear in the ecto- 

 derm, it was thought that buds would be found to spread from 

 endodermic into ectodermic territory. 



This has proven not to be the case in Ameiurus and if a study 

 of less specialized or more primitive forms shows this suppo- 

 sition to be the general rule, a view which has been advanced 

 by Johnston ('05a), the condition in Ameiurus will have to 

 be explained on the basis that the gustatory system is so highly 

 specialized that phylogenetic relationships have been materially 

 modified or obscured. 



While the results obtained do not show a derivation of ecto- 

 dermic from endodermic buds nor the reverse, as suggested by 

 Cole ('00, p. 320), still a careful study of the time of appearance 

 and the direction of spreading has brought to light a number of 

 interesting facts, which, when related to the nerve supply, throw 

 light on the problem of the distribution of ectodermic buds, if 

 they do not answer the question as to how these two groups are 

 related to each other primitively. 



I. HISTORICAL. 



The attempt to correlate the distribution of taste buds with the 

 distribution of gustatory fibers in the various cranial nerves is 

 rendered possible by two somewhat distinct lines of research. The 

 first culminated in the complete isolation, both structurally and 

 functionally, of the taste or terminal buds from all other cutaneous 

 sense organs. The second culminated in what is commonly called 

 the theory of nerve components in which we have the isolation 

 of the various components of the cranial nerves, such as the gus- 

 tatory, the lateral line and general cutaneous, based on a differ- 

 ence in the size of their fibers, and the isolation of their central 

 endings or nuclei in the brain from each other as well as on the 

 difference in types of sense organs supplied. 



