Landacre, Taste Buds of Ajneiiirus. 45 



derivation of ectodermic from endodermic buds, if it exists, dis- 

 appears. 



An attempt to explain the relation of ectodermic. to endoder- 

 mic buds should be in harmofiy with the following facts. 



First, buds situated in both endodermic and ectodermic areas 

 are supplied by communis fibers. This statement is confirmed 

 by all the workers on nerve components. Those of the oral and 

 cutaneous areas in Ameiurus are supplied exclusively by fibers 

 from the geniculate ganglion. 



Second, the number of nerve rami through which the genicu- 

 late ganglion sends communis fibers varies greatly in various 

 aquatic types (see historical sketch, p. 7, Table I), ranging from a 

 few or even only one as in the larva of Petromyzon (Johnston 

 '05) to nearly every ramus of what are commonly designated as 

 the V and VII nerves in such types as Ameiurus. 



Third, the ontogenetic method of increasing gustatory areas 

 in Ameiurus is by detached groups, spreading from anterior to 

 posterior. This indicates that the number of nerve rami through 

 which the geniculate ganglion sends fibers increases from the 

 earlier stages of Ameiurus to the later, so that the total number 

 of rami carrying gustatory fibers is not complete until more than 

 five days after hatching. The assumption involved in the last 

 statement, /'. e., that the appearance of the taste bud indicates 

 the time at which the nerve supplying it reaches the surface 

 needs verification for taste buds in Ameiurus, but has been shown 

 to be true by Szymonowicz for ('95) tactile corpuscles and later 

 ('96) for Grandry's and Herbst's corpuscles. These struc- 

 tures, according to this author, appear as the result ot the growth 

 of the nerves to the areas where they are developed and the 

 same is probably true for taste buds. The assumption is fur- 

 ther strengthened by the fact that on section of the gustatory 

 nerve in rabbits (Semi Meyer '96), the taste buds revert into 

 ordinary epithelium. The experiments of Lewis ('04) in trans- 

 planting the optic cup, and producing a lens in new areas is 

 particularly interesting in this connection. An apparent objec- 

 tion to the assumption is the disappearance of gustatory fibers 

 with the loss of superficial taste buds in terrestrial vertebrates. 

 This objection is greatly minimized, if not entirely negatived, by 

 the results of experiments on sectioning nerves (Ranson '06, 

 and his review of the literature), and the consequent retrograde 



