244 CRUSTACEA. 



vivacity, and move backwards and forwards with equal facility. 

 For want of animal substances they will 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. staphylinus, 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 does he depend upon the assertion of Miiller ? 



C. quadricornis; Monoculus quadricornis,lt. Mull., Entom., 

 XVIII, 114; Jurine, Monoc., I, II, III. All the antennae 

 simple or undivided; the inferior with four joints, and their 

 length hardly equal to one-third of the others ; the body, pro- 

 perly so called, inflated and almost ovoid; tail narrow 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. ; Ostrapoda, Straus is composed of two subgenera, 

 the first of which, Cythere, since the interesting and valuable 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., Consid., p. 364. For the other species, see the same work, p. 361 

 364, LIV ; Mull., Entom., CYCLOPS; Jurine, Hist, des Monoc., p. 1 84, 

 prem. fam. des Monoc. a coquille univalve ; Rand., Monoc., I, II, III. 



