250 CRUSTACEA. 



tail *. The ovaries are situated along the sides between this segment 

 and the first, and open separately near the back into a cavity matrix, 

 Jurinc formed betwixt the shell and the body, in which the ova 

 remain for some time after they are produced. 



Miiller has given the name of ephippium, or saddle, to a large, 

 obscure, and rectangular spot, which at certain periods and particu- 

 larly in summer, appears, after the females have changed their 

 tegument, on the superior part of the valves of the shell, and which 

 he attributes to disease. According to Straus this ephippium pre- 

 sents two oval, diaphanous ampullae, placed one before the other, and 

 forming with those of the opposite side two small oval capsules, 

 opening like that of a bivalve. It is divided, as are also the valves of 

 which it forms a part, into two lateral halves, united by a suture 

 along their superior edge ; its interior exhibits another similar, but 

 smaller one, with free edges, provided it be not the superior that is 

 attached to the valves, the two halves of which, playing upon each 

 other as if hinged, present the same ampullse as the exterior lids. Each 

 capsule contains an egg with a greenish and horny shell, otherwise 

 similar to an ordinary ovum, but requiring a greater length of time 

 for its developemcnt, and being destined to pass the winter in statu quo. 

 When the animal is about to change its tegument, the ephippium, as 

 well as its ova, is abandoned with the exuviae, of which it consti- 

 tutes a part, and which protecfrthem during the winter from the 

 cold. The heat of spring hatches them, and young Daphnise are 

 produced exactly similar to those which come from the ordinary eggs. 

 Schaeffer affirms that they will remain for a long period in a desiccated 

 state without losing the vitality of the germ, but none of those pre- 

 served in that condition by Jurine were ever hatched. They are en- 

 tirely free, or do not adhere to each other in their peculiar cavities. 

 In summer, according to Jurine, they may be hatched in two or 

 three days. In the climate of Paris, where Straus observed them at 

 all periods of the year, they require at least one hundred hours. The 

 fcetus, twenty-four hours after the production of the ovum, is a mere 

 rounded and unformed mass, on which, when closely examined, may 

 be seen obtuse rudiments of arms in the form of very short and im- 

 perfect stumps glued to the body ; neither head nor eye is perceptible ; 

 and as yet, the green or reddish body dotted with white, like the egg, 

 exhibits no motion. It is only at the nineteenth hour, and when the 

 hour has appeared, and the arms and valves are elongated, that the 

 foetus begins to move. By the hundredth hour it is very active, and 

 finally, at the hundred and tenth it only differs from the newly hatched 

 animal in the setae of the oars which are still glued to their stem, and 

 in the tail of the valves which is bent under and received between 

 their inferior edges. Towards the end of the fifth day, the tail, which 

 terminates the valves in the young animal, and the setae of the arms 

 become free, and the feet for the first time begin to move. The 

 young being ready to make their appearance, the mother lowers her 



* We omit various details of the organization, because some can only be com- 

 prehended by means of drawings, and others appear common to most of the Bran- 

 chiopoda. 



