256 CRUSTACEA. 



the two other antennae may be wanting or be obliterated in the 

 female, and form in the other sex of one of these species Chiroce- 

 pkala diaphana, Prevost those singular appendicated and dentated 

 tentacula, in the form of a soft proboscis which is susceptible of being 

 spirally convoluted, designated by Benedict Prevost under the name 

 of doigts des mains, or fingers. It is probable that, as in Apus, the 

 mouth is furnished with two pairs of jaws, a ligula and a labrum, but 

 their respective form and situation have not yet been well ascertained. 

 I am convinced that the part resembling a rostrum mentioned by 

 Schaeffer, and which Prevost calls a valve (soupape) is the labrum ; 

 that the four bodies or tubercles placed on the sides, mentioned by 

 the former, are the mandibles and the two upper jaws ; and that the 

 parts considered by the second as cirri (barbillons) are also maxillary. 

 The two first feet, which, according to Schaeffer, are composed of but 

 two joints, the last terminating in a point, would represent the two 

 first foot-jaws of the Crustacea Decapoda, and the two large anten- 

 niforrn feet of an Apus *. The chief of the male organs of genera- 

 tion, at least those which are considered as such, consist in two 

 conoid biarticulated bodies, which only project by pressure (Schaeffer), 

 situated under the second ring, in which vessels terminate that arise 

 from the first. M. Prevost presumes that the two vulvae of the 

 female are placed at the extremity of the tail, but that they afford no 

 issue to the ova. This issue (two apertures according to Schrcffer), 

 is in the second ring, and communicates internally with the sac con- 

 taining the eggs, which acts as an external 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 Chirocephcdus 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 observe 

 an ocellus, two short antennae, two very large oars ciliated at 

 the extremity, and two short slender feet, composed of five 

 joints. After the first change of tegument, the two compound 

 eyes make their appearance, the body is elongated posteriorly, 

 and terminated by a conical, articulated tail with two threads at 

 the extremity. The subsequent changes gradually developc 

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

 at first extended over and covered the abdomen, diminishes 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 

 approach of cold weather they perish. They swim with the greatest 



* See Mm. sur les Anim. sans VcrtM)., Savign. part I. 



