12 
GEOIJGE E. NICHOLES. 
Reissner’s fibre because in erubryos of Acantliias at that age 
the fibre is not developed.^ 
In this 3 'ear another paper containing a reference to 
Reissner’s fibre was published by Studnicka (’00). Replying 
to Sargent’s criticism of his former work^ he remarks that 
that author’s statements require confinnatioiq and further, 
that he himself found it very difficult to reconcile the idea of 
the fibre being a nervous structure with his own observations 
upon its relations to the V entriculus terminalis. 
This paper is also noteworthy iu that it contains the earliest 
careful figures of the modified ependymal epithelium of the 
sub-commissural organ (in the lamprey and dogfish). In his 
text the author states that he was unable to determine the 
function of this epithelium, and he does not appear in the 
least to have realised its connection with Reissner’s fibre. 
In the following April Sargent (’01) published a second 
preliminary paper, dealing this time with the development of 
the fibre, which, he said (op. cit., p. 445), “ has been studied 
in about twenty different species, and has been more or less 
completely worked out in representatives of all the chief 
groups of vertebrates.” His descriptions, however, relate 
only to Cyclostomes, Ganoids and Selachians, in which he 
claimed to have discovered “ axons ” which, growing out from 
numerous cons[)icuous nerve-cells (the “ Dachkern” of Rohoii) 
in the tectum m esen c ep h al i , emerged into the aque- 
ductus sylvii either immediately (Amiaand Petroni 3 ’zon 
marinus [?]), or after passing forward in the brain-tissue to 
the anterior end of the tectum (Selachians), these axons 
uniting in both cases in the aqueductus Sylvii to form 
Reissner’s fibre. Referring to the condition in Selachians he 
says (’01, p. 448) : “Where Reissner’s fibre leaves the brain 
tissue the mombraue covering of the roof of the ventricle is 
continued in a cone-like ])rojection surrounding the fibre 
' K:ilV)erlah, so far as I can find, nowhere states either the age or the 
size of the embryo in question. I, myself, find the fibre developed in 
the closely related Scyllinm canicula at a very early stage, and 
Sargent also records its existence early in development iu Mustelns. 
