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 ampullae, 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. Schoeffer 

 has asserted that they may remain a long time in a state of 

 desiccation, without the germ being injured; but none of those 

 which jM. 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 



