Herrick, Gustatory Paths in Fishes. 405 



pherally, have not as yet been clearly separated at their central 

 terminations, these roots must for the present retain the name 

 "communis system," pending the time when they can be sep- 

 arated into specialized (gustatory) and unspecialized visceral 

 components. With the secondary pathways and centers, how- 

 ever, the first step in this analysis may already be taken, thanks 

 to the advantages of the comparative method. 



In forms like the mammals, where the gustatory system is 

 reduced, the analysis of these two elements in the fasciculus 

 solitarius and its associated grey and secondary tracts will prob- 

 ably be impossible save by a degeneration method. The same 

 applies to the amphibia, where the term fasciculus communis 

 was first applied to the homologous structure. In fishes, again, 

 we have some forms with reduced organs of taste, where the 

 problem offers the same difficulties as in the cases cited, and 

 also forms with enormous hypertrophy of the peripheral gusta- 

 tory system with no appreciable change in the unspecialized 

 component. In the latter cases whatever enlargement of the 

 primary and secondary centers has taken place may clearly be 

 assigned to the gustatory and not to the general visceral sys- 

 tem. This is the case presented by the cyprinoid and siluroid 

 fishes particularly, where the whole of the facial lobe and its 

 connections and the greater part of the vagal lobe and connec- 

 tions have clearly arisen in response to the demands of the 

 enormous peripheral gustatory system. While the diffuse con- 

 nection of these centers with the substantia reticularis is known 

 to have a parallel in the similar connections of the fasciculus 

 solitarius of mammals and therefore doubtless in part pertains 

 to the unspecialized visceral component, the long secondary 

 paths which we here term the secondary gustatory tracts are 

 highly developed only in those fishes possessing elaborate peri- 

 pheral gustatory systems. This seems to constitute sufficiently 

 good evidence that these long paths are mainly and perhaps 

 wholly gustatory in function. 



The neurites of the chief secondary gustatory neurones of 

 the vagal and facial lobes, as we have seen, pass out in thick 

 bundles to the ventro-lateral border of the oblongata, where they 



