332 
CLASS CRUSTACEA. 
At their birth, the young ones have but four feet, and their 
body is rounded, and without a tail. Muller had formed with 
these young individuals his genus Amymone . Some time 
after (in fifteen days, from February to March) they acquire 
another pair of feet. This is the genus Nauplius 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 antennae 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 branclno-carcliac canals, of which we 
have spoken in treating of the circulation of the decapod Crus- 
tacea. It would result from several experiments of J urine 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 irritabi- 
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 antennae, the upper of 
which have much fewer articulations than in the other cyclops, 
