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at first been considered to belong to particular genera, as lias 
been observed in the case of cyclops, whose young, at differ- 
ent ages, have been named anyone and nauplia , and also in 
argulus and branchipes. 
These eggs, in one and the same species, are sometimes of 
two sorts, according to the seasons. Thus the ordinary eggs 
of daphnis are abundant and naked, while those which are to 
pass the winter at the bottom of the mud are expelled, only 
two in number, each enclosed in a capsule, with a double en- 
velope, and surrounded, moreover, with the membranaceous 
lining of the dorsal cavity, where they were first deposited. 
The parietes of this cavity are then thickened and become 
opake ; and it has appeared to some observers to be aflected 
with a peculiar malady, to w hich they have given the name of 
ephippium . 
The development of the eggs is more or less prompt, ac- 
cording to the duration of the life of the species to which they 
appertain, and the rapidity of their propagation. We have 
just seen, that in certain genera they are disclosed in the body 
of the mother. In others, they appear to grow thicker after 
being laid, before they give birth to the young, and remain in 
this state many days. There are some, in fine, such as those 
ofapus, which seem capable of being preserved dry for many 
years, without the gum which they enclose undergoing any 
alteration ; for, without this supposition, it would be impos- 
sible, unless w r e had recourse to the theory of spontaneous 
generation, to explain the sudden appearance, and in myiiads, 
after heavy rains, of those aquatic flabby Crustacea, which are 
destitute of all means of transportation, in places where, in 
the memory of man, they have never been remarked before. 
One of the most remarkable characteristics of the Crustacea 
is the reproduction of the lost members. The astaci and 
crabs are subject to lose their feet, w T hich are detached with 
the greatest facility in the joints of the articulations. A little 
