88 
GEORGK E, NICHOLES. 
cellular mass (the terminal mass of Sterzi), which is stated 
by Goette (’90, fide Favaro) to represent a solid neurenteric 
connection. Even at this age Eeissner’s fibre is visible in 
this region, and ends, apparently, in a conical terminal plug, 
the origin of which I could not determine. Although my 
smallest specimens were actually longer than those studied 
by Sargent, I believe, judging from the condition of the 
canalis centralis, that they w'ere really younger than 
his specimens. 
As I have pointed out above, it is exceedingly difficult to 
follow the fibre forwards from this point in the smallest 
specimens on account of the minute size of the central canal. 
In slightly larger specimens it is, however, possible to trace 
the fibre as a continuous thread from its origin in the brain 
to its end in the terminal sinus, but from first to last I could 
find no indication of the existence of posterior canal cells. ^ 
In one or two instances intrusive ependymal cells were found 
in the central canal, but none of these ever happened to occur 
in the sinus ter m i n al i s. 
IV. Keissner’s Fibre and the Sub-commissural Organ in 
THE MyXINOIDEI. 
'I'he heads only of some half dozen Bdellostoma (Polis- 
totreina) stouti, the common hagfish of the Californian 
coasts, were sent to me by Mr. Win. F. Allen. Of these I 
have examined the brains of four in serial section. I have 
also examined a series of sections through the head of a 
single specimen of the Cape species of hagfish, Bdellostoma 
cirrhatum (B. forsteri). The sections of this last, how- 
ever, were transverse and quite thick. Further, the stain 
employed was not the best for the purpose of this investiga- 
tion. The descriptions, therefore, of the condition in 
' An examination of a large number of specimens of other larval 
forms (an account of which will he given in subsequent parts) has given 
me similar negative results. 
