Description of the Argulus Catostomi. 303 
of reproduction. ‘Two oval yellowish vesicles or pouches, (Fig. 
1. rr.) are situated in the tail on each side of these lamine. 
The anal orifice is situated between the laminz at the base of the 
caudal sinus: the feces are conveyed through a duct lying along 
the central line of the tail, and pass out on the lower side of the 
lamine. 
The brain is situated near the upper surface of the shell over the 
sucker, and at its posterior extremity is composed of three connivent 
elliptical masses, of which two are nearly longitudinal, and the ante- 
rior transverse. The central portion between these elliptical mass- 
es, is of a deep reddish black. From the brain, nerves are given 
out, which proceed down the abdomen, and supply the natatory 
legs; below, another nerve is visible, passing to each eye. 
Posterior to the oval mass, and within the body, are observed four 
imbricated Jamine, of which the three anterior are cordate. Long 
slender cords appear to proceed from the sides of each lamina, and 
extend into the natatory legs ; those from the first lamina extending 
to the first pair of natatories, &c. These cords have much the ap- 
pearance of muscles. No blood is seen circulating in them, though 
it is very discernible, in a broad backward current over them. This 
current appears to arise from beneath the imbricate lamin, and thus 
renders it probable that they have some connection with the heart, 
if they do not actually compose it. The blood is limpid, and holds 
suspended numerous egg-shaped particles, (Fig. 8,) and is propelled 
by distinct pulsations, which occur about once in a second. The 
length of these particles is about ;,1;;th of an inch, and the greatest 
breadth about 2ths of the length. The current above referred to, 
cannot be traced along the abdomen ; but in the tail there are dis- 
tinctly apparent two parallel currents, which diverge at the base of 
the terminating sinus, and curving around the transparent margin, re- 
turn into the body. Numerous edbosditiate currents ramify through- 
out the tail, dividing it into minute areolas. 
In an upper view rof the animal, a strong current is observed above 
the heart, proceeding towards the brain, (Fig. 9.r.) where branches 
are given out to the antenne and eyes. The antennary current, af- 
ter reaching the antennz, is soon lost in the surrounding parts of the 
shell. Just below, however, on each side, appear minute branching 
* All the specimens we have seen (about thirty) have ie provided with these 
vesicles. It is possible that we have not seen any of the 
