1894 - 5 .] Cranial and Spinal Nerves of Eiasmoh^anchs. 479' 
skin and gelatinous tissue of the snout. Allis failed to find any 
branches of the Yth passing to sense organs, but recently Collinge 
has described an otic branch of the Yth passing to sense organs in 
Folyodon, We have hitherto failed to find, either in Loemargus or 
Raia, any branches of the Yth passing to sense organs. 
The Spinal Nerves. 
I. Raia . — In contrast to other Elasmobranchs, no spinal nerves 
pass through the cranium in the skate. A typical spinal nerve 
may be said to have the following dorsal branches {e.g., fig. 2, 8) : 
— (a) one from the ventral root (ventral-dorsal), closely applied tOy 
and receiving fibres from, the ganglion on the dorsal root as it comes 
up, and going with other ventral-dorsals to form a plexus dis- 
tributed to the muscles applied and dorsal to the vertebral column ; 
{h) another from the ganglion on the dorsal root (dorsal-dorsal), not 
receiving any fibres from the ventral-dorsal, and distributed to the 
skin. Whilst the greater proportion of the spinal nerves of the 
skate may be resolved into the above elements, there is still a very 
considerable amount of variation, and fig. 2 is a semi-diagrammatic 
representation of the anatomy of the first 13 spinal nerves of a 
single specimen of R. batis, in which the following variations were 
observed : — (1) ventral-dorsals 1, 2, 3, very much larger than the 
others. Nps. 1 and 2 are sometimes described as the ventral roots 
of the vagus, but they are distinctly spinal nerves, though possessing 
no dorsal roots ; (2) ventral-dorsals 3 and 7, immediately after their 
origin, divide into two large nerves, which do not assist in forming 
the muscular plexus ; (3) ventral-dorsal 5 accompanies dorsal-dorsal 
4 instead of 5 ; (4) ventral-dorsal 6 divides into two branches — one 
accompanying the dorsal-dorsal, and the other assisting in the for- 
mation of the muscular plexus ; (5) ventral-dorsal 10 passes through 
the edge of the ganglion on the dorsal root — (on other specimens 
it was demonstrated, both by dissections and sections, that the ventral- 
dorsal passed right through the ganglion, but this is certainly 
unusual); (6) ventral-dorsal 11 unites with the dorsal-dorsal; (7) 
ventral-dorsals after 10 were extremely fine, and could only be 
traced with great care ; (8) there were two dorsal-dorsals on 10 and 
12, and three on 13. 
