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 Jmine 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." 



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 setau. 



