332 CLASS CRUSTACEA. 



At their birth, the young ones have but four feet, and their 

 body is rounded, and without a tail. Miiller had formed with 

 these young individuals his genus Amyinone. Some time 

 after (in fifteen days, from February to March) they acquire 

 another pair of feet. This is the genus Naupliiis of the 

 same. After the first moulting, they have the form and all the 

 parts which characterize the adult state, but with smaller pro- 

 portions. Their antennaj and their feet are proportionally 

 shorter. At the end of two other moultings, they are fit for 

 generation. Most of these entomostraca swim upon the back, 

 leap with vivacity, and can go backwards as well as forwards. 

 In default of animal matters, they attack vegetable substances ; 

 but the fluid in which they live habitually does not pass into 

 the stomach. The alimentary canal extends from one extre- 

 mity of the body to the other. The heart, in the cyclops cas- 

 tor is immediately situated under the second and third seg- 

 ment of the body, and ovaliform. Each of its extremities 

 gives birth to a vessel, one of which goes to the head and the 

 other to the tail. Immediately under it is another analogous 

 organ, but pyriform, producing also, at each end, a vessel, per- 

 haps representing the branchio-cardiac canals, of which we 

 have spoken in treatingof the circulation of the decapod Crus- 

 tacea. It would result from several experiments of Jurine upon 

 Cyclopes, alternately asphyxiated, and restored to life, that in 

 this sort of resurrection the extremity of the intestinal canal 

 and the fulcra give the first sign of life ; and that the iiTitabi- 

 lity of the heart is less energetic. That of the antennae, and 

 more especially of those of the males, of the palpi, and of the 

 feet, is inferior. When a portion of the antenna is cut away, 

 no organic change is effected. The reparation takes place 

 under the skin, since this organ re-appears perfectly entire at 

 the next moulting. The cyclops staphylinus forms a particu- " 

 lar division, by reason of its shorter antennge, the upper of 

 which haveiuuch fewer articulations than in the other cyclops, 



