264 Journal of Comparative Neurology. 



from the root-border grow, with a participation in the prin- 

 cipal ganglion then originating, over into the ventral region 

 (Fig. ^, nd). It there connects secondarily with a portion 

 proceeding from the distal end of the associated principal 

 ganglion, of which I cannot definitely say whether it is of 

 central or of epidermal derivation — that is to say, whether 

 it is derived from the medial or lateral part of the ganglion, 

 or from both. Then, later, when the epibranchial ganglia 

 arise, further complications ensue. In conjunction with the 

 formation of these ganglia, there appears a peculiar sub- 

 epidermal layer of cells, which gradually spreads from the 

 eye to the hindermost gill pouch, dzif remains conjined to thc 

 ventral side. 



If it were not preoccupied, I would suggest the name 

 "hypodermis" for this layer, but, as it is, propose the term 

 " neurodermis" (Figs. 6, 7, 10, nb). The point of origin of 

 this structure is the vicinity of earliest epibranchial ganglion, 

 dorsad and cephalad of the second gill pouch. At the lateral 

 line, i.e., the outer boundary between the dorsal and ventral 

 region, the neurodermis is not strongly developed; here it 

 consists of several layers of cells which form an inwardly 

 projecting ridge, but in general it remains one-layered and 

 consists of closely arranged but disconnected epithelium-like 

 cells, with a prevailingly cylindrical form. 



Note. — The figures which are referred to in this paper will be 

 collected in plates at the end of the article. 



[to be CONTINCE]).] 



