342 
CLASS CRUSTACEA. 
of the year, and particularly in summer, shows itself, after the 
moulting of the females, at the upper part of the valves of the 
shell, and which Jurine attributes to a malady. According 
to M. Straus, this ephippium presents two ovaliform bubbles, 
transparent, placed one before the other, and forming with 
those of the opposite side two small oval capsules, opening like 
a bivalve capsule. It is divided, as well as the valves of which 
it forms a part, into two lateral moieties, united by a suture 
along their superior edge. Its interior presents another simi- 
lar one, but smaller, with the edges free, except the superior 
one, which attaches to the valves, and the two moieties of 
which, playing like a hinge one upon the other, present the 
same ampulla), as the exterior valves. Each capsule encloses 
an egg, with a horny and greenish shell, similar in other re- 
spects to the common eggs, but remaining longer without being 
developed, and passing the winter under this form. At the 
period of moulting, the ephippium, along with its eggs, is aban- 
doned, with the exuvia of which it forms a part. It serves as 
a shelter for these eggs during the cold. The heat of spring 
causes them to disclose, and little ones come forth, absolutely 
similar to those produced from the common eggs. Schceffer 
has asserted that ihej may remain a long time in a state of 
desiccation, without the germ being injured ; but none of those 
which M, Straus preserved in that state disclosed. They are 
absolutely free, or without adhering to each other, in the cavi- 
ties which are proper to them. According to Jurine, they may 
disclose in summer at the end of two or three days. Under 
the climate of Paris, where M. Straus has observed them at 
all periods of the year, they require at least one hundred hours. 
The foetus, twenty hours after the egg is laid, presents nothing 
but a rounded and unformed mass, on which may be remarked, 
on close examination, the obtuse rudiments of arms, in the 
form of very short and imperfect stumps, cemented against the 
body. Neither head nor eye are visible. The body, green or 
