M.T. Thorell on two European Argulide. 167 
this point. That one of the anterior pairs of nerves runs into 
the second pair of tootjaws, that, moreover, out of the lateral 
bundles a nerve proceeds to each leg, and that the last (inner- 
most) pair of nerves passes unbranching to the tail, I have, how- 
ever, ascertained. No doubt certain stems proceed to the head- 
shield, although I have not been able to follow them thither. 
Of the two pairs of nerves which radiate from each of the second 
to the fifth ganglia, the foremost, which is also the thickest, pro- 
ceeds from the margin of the ganglion, the hinder one from its 
underside. The nerves of the sixth ganglion are almost equally 
strong ; those of one pair start from its side, those of the other 
from its hinder margin. 
The eyes seem to be entirely similar in structure to those of 
A. foliaceus. The number of crystalline cones I have found to 
vary between 40 and 50. ‘The single eye-spot consists of pig- 
ment only, without crystalline bodies. 
The intestinal canal.—The narrow, chitinous gullet proceeds 
in a bowed shape to the stomach, where it opens, by means of a 
cup-like organ, into a cardia, which, however, is longer and 
narrower than in A. foliaceus. The length of this organ is about 
0:33, its greatest breadth 0-15, and its least breadth 0-09 millim. 
The mouth of this organ is thickly set with papilla or obtuse 
teeth. Before its entrance into this latter the gullet shows an 
increase of width (its greatest diameter being about 0:06 millim., 
its diameter where it enters the cardia about 0°04 millim.). 
The stomach itself is a short, spacious, posteriorly rounded 
sac, which passes into the intestine between the first two pairs 
of swimming-feet, being, however, distinctly separated therefrom. 
On either side the stomach sends forth a strong branch into the 
head-shield ; the further outbranchings of this are not easily fol- 
lowed in a specimen in spirits ; and therefore I cannot venture to 
state whether such branches are directed outwards only, as in 
A. foliaceus, or whether, as in A. purpureus, they proceed from 
the larger stems inwards as well as outwards. 
The intestine extends as a spacious, gradually tapering tube 
from the stomachal sac to the anal opening, which is situated 
between the appendages of the tail. 
The heart or dorsal vessel I have not been able to separate 
distinctly. I regard the tail as a respiratory organ which, on 
its inner surface, shows a copious network of muscular fibres, 
the contractions of which keep the nourishing fluid in quick and 
powerful motion. 
Generative organs.—In full-grown females the ovary forms an 
oval mass, which extends from the base of the second pair of 
footjaws to the base of the tail, where the opening is situated in 
a low rounded projection. The surrounding membrane stretches 
