Description of a Species of Caligus. 261 
place over the whole surface of the body. It is stated by Straus, 
that on separating the branchice of a lobster, the body absorbed 
nearly one half the oxygen usual before the removal of these or- 
gans. The thin envelop of the Caligus, and the extent of its 
external surface, must render its body a far more perfect substitute 
for branchiz than the solid covering of the lobster. The vibra- 
ting action of the natatory legs serves to keep up a constant cur- 
rent of water, and thus affords continually a new portion to 
undergo the respiratory action of the body. It might be re- 
marked that these legs, on account of their breadth, could not act 
so as to produce this current of water, when the whole margin 
around is attached. Probably the animal is not thus attached 
except when it is rendered necessary by the swift motion of the 
fish ; under which circumstances, there is a sufficient current, 
without the action of these legs. We may presume that the spe- 
cial object of these marginal cups is to enable the animal to attach 
itself, and still keep the principal part of its body free, so that 
these natatory legs, when the fish is motionless, may have space 
to act, and sustain a continued current. 
V. Organs or Repropuction. 
On each side of the stomach, there is a large pyriform organ, 
(Pl. V, fig. 18,) of a glandular appearance internally, and provi- 
ded with a distinct duct, which at first we unhesitatingly pro- 
nounced. the liver. Subsequent observation proved that the duct, 
which we had supposed to enter the intestine, extends through 
the whole length of the thorax into the abdomen, where it is con- 
, in the male, with organs known to be taaaais and in 
the female, with the egg-bearing vessels. 'These organs, thus 
shown to be connected with the organs of generation, have been 
since proved to correspond with the spermatic glands in the male 
and the ovaries in the female. 
In the male, they are rather larger than the buccal mass, (PI. 
V, fig. 21,) and are situated just anterior to the stomach, in part 
beneath the base of the prehensile legs and the spine of the pre- 
ceding pair. Their small posterior extremity is produced into a 
short ligament, by which it adheres above the stomach; the an- 
-terior portions are so enveloped in their cellular or iadabetsions 
attachments, that they are separated with great difficulty. In 
general appearance, it resembles a pyriform membranous sac, 
