6o NERVE COMPONENTS OF BONY FISHES. 



sensory terminal clusters, nor two separate portions for 

 the two nerves. A single root, common to both nerves, 

 passes over into the fasciculus solitarius without loss of 

 any fibres, in such a way that between the upper, or chief 

 nucleus, and the lower, or descending nucleus, there is no 

 distinction aside from that of position." 



The preceding considerations, it seems to me, remove 

 the difficulties raised by Kingsbury, regarding the hom- 

 ology of the fasciculus solitarius of mammals with the 

 fasciculus communis of the Ichthyopsida. He questions 

 this homology ('95, p. 173) because, among other reasons, 

 "by considering the fasciculus conununis as representing 

 the fasciculus solitarius alone, we leave unaccounted for 

 the larger end-nidus of vagal sensory fibres. Strong, 

 apparently, confounds this with the end-nidus of the fas- 

 ciculus solitarius y This position he reiterates in his later 

 paper ('97, p. 31). There is, it is evident, a certain 

 amount of confusion in the recent literature regarding this 

 homology. It is equally evident that this confusion is 

 largely a matter of definition. If we use the terms fas- 

 ciculus communis and fasciculus solitarius in the narrow 

 sense, as longitudinal fibre tracts, and if we rigidly define 

 the related structures, especially the terminal nuclei, and 

 take into account the various transformations which the 

 latter undergo in different classes of vertebrates (particu- 

 larly Cajal's results cited above), it appears that in the 

 broad view the fasciculus solitarius and its related struc- 

 tures in the mammals are, taken as a whole, homologous 

 with the fasciculus communis and its related structures in 

 the Ichthyopsida, though if we should attempt to draw up 

 a detailed comparison, the various elements would doubt- 

 less not be exactly equivalent in the two groups of ani- 

 mals. Indeed, the fasciculus communis is, as we have 



