DAPHNIADiE. 
71 
The posterior of the two branches is divided, in most 
of the species, into four articulations, and the anterior 
into three. Both branches are furnished with several 
long filaments or setae, which, in some of the species, as 
the pulex , are beautifully feathered, or plumose, and con- 
sist each of two moveable joints, which augment their 
flexibility. Swammerdam calls these organs the arms, 
and describes their motion very particularly, which, he 
says, is threefold ; rectilinear , up and down, and to each 
side ; unequal , keeping the animal now at the bottom, and 
then at the top of the water, which sort of motion he 
compares to the flight of a sparrow; and gyratory , by 
which the animal moves itself in a circular manner. 
De Geer also calls them arms; but Muller, and most 
other naturalists after him, call them antennae. Jurine, 
however, calls them “bras ramifies,” and Straus, consi- 
dering them as the chief or almost only organs of loco- 
motion, and acting as it were as fins, calls them rami or 
“rames branchues ;” they are, in fact, he says, a first pair 
of feet, and act as such, as it is by means of these organs 
alone that the animal moves, the other feet not serving at 
all for that purpose. 
The eye (t.VIII, f. a, b, c) is a spherical body, furnished 
with powerful muscles, so arranged as to allow it to pos- 
sess a semi-rotatory motion upon its centre, and is com- 
posed of about twenty crystalline lenses, which are limpid, 
and when isolated are each pear-shaped. Swammerdam 
asserted that there were two eyes, which seemed to be 
joined together, and several authors have adopted the 
same opinion. Schoeffer, however, says there is only one, 
and Muller and De Geer repeat this, — an opinion which 
has also been adopted, and proved correct by Straus and 
J urine. Eichhorn, as quoted by Straus, mistook the eye 
for the stomach ! 
The brain, or first ganglion of the nervous system, is 
situate near the eye, and is composed of two lobes, from 
the superior anterior commissure of which we see, going 
off to the eye, the optic nerve. The mouth (t. VIII, f. b) is 
