104 
GEORGE E. NICHOLES. 
long ago as 1894. That author was the first to trace the fibre 
forwards into the rnid-brain and backwards into the sinus 
terminalis, and he, too, was the first to point out that the 
caTial centralis was widely open posteriorly (in Myxine), 
and that through this opening Reissner’s fibre passed. 
Apparently he had formed no definite opinion as to the 
character of this ‘‘central rod,” as he called it, in Myxine, 
although in an earlier paper he had accepted Stieda’s dictum 
that it was merely an artifact. 
His account of the splitting of Reissner’s fibre in the 
fourtli ventricle into two portions, one of which passes 
through the isthmic canal and the other through the lower 
canal (the ventricular canal of my descriptions), is, however, 
erroneous. It is true that in material that is not well 
preserved there is found a quantity of coagulum which pre- 
sents the appearance of a network of fil)res, and which might 
be mistaken for Reissner’s fibre. In well-presei'ved material, 
however, this is absent, and the unmistakable fibre stretches 
tautly from its point of origin in the anterior part of the 
sub-commissural canal through the upper portion of the 
sinus m e s ocoe 1 i c u s, and thence through the isthmic canal, 
nowhere receiving any conspicuous factor or giving off any 
important branch. The ventral portion of the sinus meso- 
coe liens and the ventricular canal are not in any of my 
specimens traversed by the fibre of Reissner. Indeed, I 
have suggested that the portion of themesocoel which I have 
termed the isthmic canal has persisted in Myxine (when 
other portions of the brain-ventricles have been obliterated) 
because it is traversed by Reissner’s fibre. 
Studnicka, whose findings, in other respects, confirm those 
of Sanders, says nothing of any part of the fibre passing else- 
where than through the isthmic canal. 
The only other observations upon Reissner’s fibre in 
Myxinoids are, I believe, those recorded by Ayers (’08). 
Although he does not refer to it by that name, but speaks 
mei-ely of “ventricular fibres,” I think that there can be no 
doubt that it is to Reissner’s fibre that his work relates. He 
