256 
CRUSTACEA. 
the two other antennse may be wanting or be obliterated in tlie 
female, and form in the other sex of one of these sjjecies— C'AiVoce- 
phala diaphana, Prevost — those singular appendicated and dentatcd 
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. 
'J'he 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- 
niform 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 Schaeffer), 
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, appeal's 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 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 develope 
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 Mem. sur les Anim. sans Vert^b., Savipn. part I. 
