136 
Proceedings of the Royal Society 
Monday, 2 d June 1873. 
Sir ROBERT CHRISTISON, Bart., President, in 
the Chair. 
The following Communications were read: — 
1. On the Anatomy of a new species of Polyodon,the Polyodon 
Gladius of Martens, taken from the river Yang-tsze-kiang, 
450 miles above Woosung. Part II., being its Nervous 
and Muscular Systems. By P. D. Handyside, M.D. 
( For a notice of Part I., see p. 50). 
The author showed to the Society a small entire specimen of the 
P. gladius , and next described, from a larger opened and dissected 
one, and from part of an adult fish, the spinal cord, the brain, the 
organs of the senses, and other parts of its nervous system. He 
illustrated his remarks by exhibiting four large drawings and nine 
smaller ones, including six microscopic views, explanatory of his 
description of the structure and disposition of the spino -cerebral 
axis , the encephalon as viewed from above and below, the ramifi- 
cations of the encephalic-nerves, and more particularly the struc- 
tures subserving the senses of smell, sight, and hearing. A 
cartilaginous capsule forms the olfactory chamber, the mesial half of 
which is occupied by a fibrous disk composed of 29 septa which 
radiate from a prominent modiolus, and thus leave intermediate 
pituitary pouches, consisting of pigment cells and sarcole, invested 
with tapering, probably ciliary, epithelium. The choroid of the 
eye is connected with the exterior of the sclerotic by means of two 
large tubular processes that may be regarded, anatomically, as a 
modified form of the vaso-ganglion or choroid gland found hitherto 
in most osseous fishes only. The cysticule and utricule of the 
auditory apparatus are the only parts of the labyrinth that open into 
the cranial cavity, — differing thus from the generality of bony 
fishes and from sturgeons. A remarkable sinus impar is present, as 
in some osseous fishes; it is situated in the middle line of the skull, 
and connects the right and left vestibules through their upper walls. 
