102 
GEORGE E. NICHOLES. 
rather narrow vertical cleft. Tlie spinal cord itself turns 
downwards behind the end of the notochord and becomes 
enlarged to partly enclose the large sinus terminalis. I 
was able to make out this condition in but one of the three 
tails examined in sagittal section ; the other two had become 
twisted during the preparation of the material for sectioning, 
and in consequence were cut so obliquely as to be un- 
intelligible. 
Both Sandei'S and Studnicka seem also to have found 
such a terminal sinus, and there appears to be no reason to 
doubt that this is the normal condition of the end of the 
spinal cord. 
In the one specimen examined, the walls of the sinus are 
clothed antero-dorsally by the ependymal epithelium of the 
canalis centralis, but posteriorly the space is enclosed onlv 
by the connective tissues of the meninges. We have thus in 
Myxine a sinus terminalis into which the canalis 
centralis opens by a terminal neural pore exactly as in the 
P e t r o m y z 0 n t i d ae . 
Through this terminal neural pore Reissuer’s fibre passes, 
and, in the one specimen in which the relations of these parts 
could be clearly made out, ends in a large intricately coiled 
mass, which Sanders has aptly described as a “ a mulberi-y- 
like mass of glass-like aspect.” 
A central section through the mass is shown in fig. 18, 
which is reproduced from an actual photomicrograph. The 
sections had been slained simply with borax-carmine in bulk, 
and the mass of fibre was only faintly tinged with pink. 
After the photomicrograph had been taken the sections were 
double-stained with picro-indigo-carmine. The coiled terminal 
mass of fibre became stained green or blue-green in a manner 
absolutely unlike that in which a nerve-fibre stains. Another 
photomicrograph was taken, this time of a section nearer to 
the surface of the mass, and is reproduced as fig. 17. This 
shows some loose coils of Reissner’s fibre lying near the apex of 
the mass, and close to the opening of the terminal neural pore. 
'riie photomicrographs are not nearly as perfect as I could 
