322 
CLASS CRUSTACEA. 
conduct by gradual shades to the lerna39e ; but the presence of 
eyes, the faculty of changing skin, or even of undergoing a 
sort of metamorphosis, the power of being able to transport 
themselves from one place to another by means of the feet, 
appear to us to establish a positive line of demarcation be- 
tween these last animals and the preceding. We have con- 
sulted with respect to these transformations, different well 
informed naturalists, who have had frequent occasions of ob- 
serving the lernaeae, and none have ever witnessed any 
change of skin among them. It is true, indeed, that the 
young of daphnise, and of some other neighbouring subgenera, 
those probably also of cypris, and of cytherea, on issuing 
from the egg, scarcely differ from their parents, except as to 
size; but those of Cyclops, of phyllopus, of argula, undergo 
notable changes in their early age, either in the form of the 
body, or the number of the feet. In some, such as the argulae, 
these organs even undergo transformations, which modify 
their uses. 
The antennae of the entomostraca, the form and number 
of which vary much, answer, in many of these animals, the 
purpose of swimming. The eyes are very rarely supported on 
a pedicle, and when they are, this pedicle is but a lateral 
elongation of the head, and never articulated at its base. 
They are often very closely approximated together, and often 
compose but a single eye. The organs of generation are situ- 
ated at the origin of the tail ; and it is erroneously that 
the antenna) of some males have been considered as the seat 
of them. This tail is never terminated by a fan-like fin, and 
does not present those false feet, which we have observed in 
the malacostraca. The final feet, indeed — if we except the 
phyllopoda — are thoracic, or jaw- feet. The eggs are accumu- 
lated under the back, or they are external, and under a com- 
mon envelope, in the form of one or two small clusters, situated 
at the base of the tail. It appears that they may be pre- 
