BRANCHIOroDA. 
243 
tlie anterior pair, corresponding to the second jaws, differs slightly 
from those that follow. Jvirine compares it to a kind of hands. To 
each of the three following segments is attached a pair of feet formed 
like the last of the preceding ones. Two of the antennae, superior 
to the others, are longer, setaceous, simple, and composed of nu- 
merous small joints ; by their action, they facilitate the motion of 
their body, and almost perform the office of feet. The inferior — 
antennales, Jurine — are filiform, usually jiresent but four joints, arc 
sometimes simple, and at others, forked; by the rapidity of their 
motions in the water, they occasion a kind of wliirlixiol. In the males, 
the superior antennae or one of them only ( C. castor') are marked by a 
sti’angulation and dilatation, followed by a joint with a hinge. By means 
of these organs, they seizetheir females, in theiramorous preludes, either 
by the posterior feet, or by the extremity of the tail, and keep tliem, no- 
lens volens, in the peculiar position in which they fix themselves. The 
latter carry off the males, when they are unwilling to gratify their 
desires on the spot. The business of coition is performed, as in the 
preceding Crustacea, and by pz’ompt and repeated acts. Jurine observ- 
ed it to occur three times in the space of fifteen minutes. Until the pub- 
lication of his remarks, it was thought that the male organs of genera- 
ion were placed on the superior antennse, and this error aj>pearcd to be 
the more probable, inasmuch as an analogous conformation was 
known to exist in the Araneides. On each side of the tail, in the 
female, is an oval sac, filled with eggs — ovaii’c externe, Jurine-— ad- 
hering by a very slender pedicle to the second segment, close to its 
junction with the third, where the orifice of the oviduct is also visible. 
The pellicle, forming these sacs, is a mere continuation of that of 
the internal ovary. The number of ova they contain augments with 
age ; they are at first broAvn or dark, afterwards become reddish, and, 
when the young ones are about to be hatched, are almost transparent, 
but without increasing in size. If insulated or detached, at least 
until a certain period, the germ perishes. A single, but indispensa- 
able fecundification suffices for several successive generations. The 
same female may spawn ten times in the space of three months. Al- 
lowing it to occur but eight times in that period, and the number of 
young ones produced to be forty, the sum total of births will amount 
to near four thousand five hundred millions. The length of lime 
which the young remain in the ovaries, varies from two to ten days, 
according to the temperature of the season, and various other circum- 
stazices. The oviferous sacs sometimes present a greater or less 
number of elongated glandiform bodies which appear to consist of a 
collection of Infusoria. 
The young, at birth, have four feet, and their body is rotuided and 
without a tail. It was with these that Muller formed his genus 
Amymone. Some time after — fifteen days, from February to March 
— they acquire another pair of feet, constituting the genus Naupfiu^, 
Muller. After the fii’St change they have the form and all the parts 
which characterize the adult animal, but more exiguously proi)or- 
tioned ; their antennae and feet are proportionally shorter. After 
thrice changing their skin they are ca])able of propagation. Most of 
these Entomostraca swim on tlieir back, dart aizout with great 
p, 2 
