244 
CRUSTACEA. 
vivacity, and move backwards and forwards witli equal facility. 
For want of animal substances they Avill attack vegetable matters, but 
the fluid in which they live does not pass into their stomach. The 
alimentary canal extends from one extremity of the body to the 
other. The heart in the C. castor is oval, and situated under the 
second and third segments of the body ; a vessel is given off at each 
of its extremities, one running to the head, and the other to the tail. 
Directly under it is a second analogous, but pyriform organ, which 
also produces a vessel at each end, corresponding perhaps to the 
branchio-cardiac canals, mentioned in our observations on the circu- 
lation of the Crustacea Decapoda, From several experiments made 
by Jurine upon various Cyclopes, alternately asphyxiated and resus- 
citated, it would appear that in this sort of resurrection the extremity 
of the intestinal canal gives the first signs of life, and that the irri- 
tability of the heart is less energetic ; that of the antennae, in the 
males especially, of the palpi, and lastly of the feet, is inferior. No 
alteration is effected in the antennae by amputating a portion of them ; 
the reintegration takes place under the skin, for the organs reappear 
in all their entireness at the ensuing moult. 
The C. slaphylinus, from its shorter antennae, the superior of 
which consist of a considerably less number of joints than those of other 
Cyclopes, while the inferior, on the contrary, have more ; and from the 
shape of its body which gradually diminishes towards its posterior ex- 
tremity, so that it seems to have no tail or at least none that is abruptly 
formed, and its back, in the females, being armed with a kind of horn 
posteriorly arcuated, forms a particular division. The C. castor, and 
some others whose inferior antennae and mandibular palpi are divided 
above their base into two branches, may also compose another group. 
The one designated by Leach under the general name of Calanus, 
might in fact constitute a separate subgenus, if it were true that the 
animal on which it is founded had no inferior antennae ; but has that 
gentleman satisfied himself that such is the fact, by personal observa- 
tion, or docs he depend upon the assertion of Muller ? 
C. quadricornis', Monoculus quadric or nis,\j.'. Mull., Entoni., 
XVIII, 1 — 14; Jurine, Monoc., I, II, III. All the antennae 
simple or undivided ; the inferior Avith four joints, and their 
length hardly equal to one-third of the others ; the body, pro- 
perly so called, inflated and almost ovoid; tail narroAV and formed 
of six segments. The colour varies greatly ; some are reddish, 
others whitish or greenish. The whole length of the animal is 
two lines. This species is very common *. 
The second general division of the Lophyropa Branchiopoda, or 
that in which the shell is formed of two valves uniting by a hinge — 
OsTRACODA, Lat. ; Oslrapoda, Straus — is composed of two subgenera, 
the first of which, Cythere, since the interesting and vahiable obser- 
vations of the latter upon the second or Cypris, appears to solicit a 
more profound examination than that of Muller, our only authority 
• Desmar., Consul., p. 364. For the other species, see the same work, p. 361 
— 364, LIV ; Mlill., Eutom., Cyclops; Jurine, Hist, des Monoc., p. 1 — 84, 
prem. fam. des Monoc. a coquillc univalve ; Rand., Monoc., I, II, III. 
