136 CRUSTACEA. 



matrix. But there is no crustaceous animal known in which the 

 female organs of generation are placed at the posterior extremity of 

 the body, and hence we can allow but little weight to this opinion. 



The observations of Schaeffer on the hairs of the feet of these 

 Crustacea, prove that they are so many air tubes; even the surface of 

 the feet of which they are composed, appears to absorb a portion of 

 the air which adheres to it under the form of little bubbles. 



The Chirocephalus diaphanus, Bened. Prevost, which seems to 

 us to be very closely allied to our Branchipus palustris, if it be 

 indeed different, has, when first hatched, a body divided into 

 nearly equal and almost globular masses. In the first we ob- 

 serve an ocellus, two short antennae, two very large oars ci- 

 liated at the extremity, and two short, slender feet composed 

 of five joints. After the first change of tegument the two com- 

 pound eyes make their appearance, the body is elongated pos- 

 teriorly, and terminated by a conical, articulated tail with two 

 threads at the extremity. The subsequent changes gradually 

 develope the feet, and the oars disappear. The valve soupape 

 which at first extended over and covered the abdomen, dimi- 

 nishes in proportion. 

 The Branchipi are found, and usually in great numbers, in little 

 muddy, fresh water pools, and frequently in those that are formed 

 by heavy rains, particularly in spring and autumn. On the first ap- 

 proach of cold weather they perish. They swim with the greatest fa- 

 cility on their back, and their feet, which they cannot use for walking, 

 while thus employed, present a graceful and undulating motion. This 

 motion creates a current between them, which, following the canal 

 of the thorax, directs to its mouth the atoms which constitute its- 

 food; when the animal wishes to advance it strikes the water, right 

 and left, with its tail, which forces it forwards by bounds and leaps. 

 Withdrawn from its element, it moves its tail for a while, and curves 

 itself into a circle. Deprived of a certain degree of humidity, it re- 

 mains motionless. 



Benedict Prevost states, that when the male of the species which 

 constitutes the object of his memoir seeks his female, he swims 

 round her, seizes her by the neck with the two horn-like appendages 

 of his head, and remains fixed there, until she turns up the posterior 

 extremity of her tail, in order to approximate the two valves of the 

 copulating organs; this process is analogous to the coitus of the Li- 

 bellulae. The ova are yellowish, spherical at first, and afterwards an- 

 gular; the shell is thick and hard, a circumstance which lends to 

 preserve them. It appears that even desiccation, provided it be not 

 carried too far, produces no change in the germ, and that the young 

 are hatched as soon as a sufficiency of rain has fallen. M. Desmarest 



