ARGULUS. 
251 
matrix is contained in the thoracic portion of the body, 
and in a gravid female the whole cavity of the thorax is 
occupied with the eggs. These escape by a very short 
oviduct, whose orifice is placed between the two natatory 
feet. 
The male organs have been described by Jurine, and 
he appears to have been the first to detect them ; indeed 
they have not been described by any other individual. 
According to this author, they are situate on the last two 
pairs of feet. On the anterior edge of the first joint of the 
fourth pair, and close to its extremity, there is a brown 
conical tubercle of a horny nature, the base of which is 
armed with a small hook directed backwards. Corre- 
sponding to this, we find on the posterior edge of the first 
ring of the preceding, or third pair of feet, a vesicle filled 
with transparent liquid; apparently, says Jurine, destined 
for fecundation. The male organs are thus double. The 
circulation of the blood can be distinctly seen in several 
parts of the body. The blood is a transparent fluid, com- 
posed of small, round, diaphanous globules, and is pro- 
pelled to the different parts of the body by distinct pulsa- 
tions, which occur about once every second. 
The Argulus in this country is found upon various fresh- 
water fishes. In the neighbourhood of London it is most 
commonly to be met with upon the stickleback ; but it has 
been taken also upon the carp and the roach ; and in other 
places it has been found upon the trout, the pike, the 
perch, and even upon the tadpole of the common frog. 
An individual taken from the salmon trout at Belfast, 
by Mr. W. Thompson, was placed by him in water in 
which salt was dissolved, till it became to the taste like 
sea- water, and it remained for four or five hours active and 
lively. 
The species which has been described by Dana and 
Herrick, in North America, was taken from the fish 
called the Sucker, in the water of Mill River, near Whit- 
ney ville, into which the tide from Newhaven Harbour 
