188 
BRITISH ENTOMOSTRACA. 
but varying very much in the different genera. Attached 
to the next three segments of the thorax, and arising 
from the interstices between each, we find three other 
pairs of double feet, in general resembling each other 
exactly, and adapted solely for the purpose of swimming. 
The fifth pair is very small, nearly rudimentary. It is 
attached to the first segment of the abdomen, and is 
larger in the female than in the male. It differs some- 
what in appearance in the different species, and as its 
use was supposed by Jurine to be, to give support to the 
oviducts which furnish the envelope of the external ovaries, 
has been called by him “ les supports ou fulcra / 7 
The female organ of generation or vulva is placed in the 
abdomen also, at the junction of the second segment with 
the third; this opening forms also the mouth of the 
canalis deferens , which communicates directly with the 
internal ovary, and gives passage to the eggs. In most 
of the species the male organs appear to be situate in the 
first segment of the abdomen, though in the Cyclops 
quadricornis we find them in the second. The external 
ovary, or bag of eggs, springs from where the second 
segment articulates with the third, and is attached to it 
by a very slender pedicle. The internal ovaries consist 
of an opaque mass of solid looking matter, composed of 
numerous round globules of a dark-brown colour, dis- 
posed round the alimentary canal, and occupying a con- 
siderable space of the interior of the body. This, as I 
have already stated, has a direct communication with the 
opening at the junction of the second with the third 
segment of the abdomen, the canalis deferens of Jurine ; 
and it is through this canal that the eggs pass into the 
external ovary. 
The alimentary canal is very perceptible, beginning 
behind at the place which I have mentioned as the situa- 
tion of the lips, and terminating at the extremity of the 
abdomen where the tail commences. The tail consists 
of a bifid segment, which is generally short and terminates 
in two or more long setae. 
