304 Description of the Argulus Catostomt. 
vessels, in which the blood has a returning course. ‘These minute 
vessels discharge themselves in a broad channel, (Fig. 9. n.) which 
enters the body near the base of the abdomen. 
The ophthalmic current, which is most distinctly seen in an under 
view, curves at the eye and passes backward, enters the suction legs, 
is seen again between those legs and the prehensile, and also fora 
short distance posterior to the latter, after which it disappears. 
Another current (Fig. 9. k.) goes out laterally, a short distance be- 
hind the brain, to the anterior margin of the reniform area before 
described. It passes just within the exterior margin of the same 
area, and returns into the body after a final course along the inner 
edge of each lobe of the shell. 
Near the base of the abdomen arises a fourth current, which run- 
ning downward and outward is diffused through the lower portions 
ef the shell, and probably returns into the body by the same cur- 
rent with the preceding. 
It is impossible to trace the passage of the blood into the.bran- 
chial legs. It is probable that the above currents, after returning 
to the body, pass to these legs for aeration, and thence to the heart 
to be again diffused throughout the animal. Pulsation is frequently 
observable along the whole abdomen, and often with great distinct- 
ness in the tail. The currents of blood are not apparently confined 
within vessels of definite limits. 
The pairs of muscles by which the animal moves the various parts 
of the shell are four. The first, or that acting on the clypeus, arises 
each side of the brain and accompanies the antennary blood vessels. 
The second (00) arises just below the base of the preceding, and is di- 
rected outward and upward. Between this and the third is a suture, 
which is apparent when either muscle is in action. The third ac- 
companies the current of blood (k) which passes to the anterior part of 
the reniform area. The fourth accompanies the current (m) which 
flows to the posterior portion of the shell, and is attached near the 
central part of this portion. Several of these muscles are easily 
mistaken for the courses of the blood. The muscles of the legs are 
for the most part visible, and are given in the plate. ‘Two muscles 
extend from their insertion, near the base of the prehensile legs, on 
each side of the abdomen, and appear to cross near its extremity- 
r The entire abdominal region below of the gravid female, is occu- 
Ss y eggs. The number of eggs which may be laid by one fe- 
male, cannot be stated with certainty. On the 18th of June, 1936, 
