Anatomy of Daphnia. 253 



sidered by Schaeffer as pockets filled with a liquid destined 

 for the reproduction of the shell at each moulting. This 

 opinion, however, has never been verified by any succeeding 

 observer. Till Jurine and Straus described these insects, the 

 number of the pairs of feet even seemed to be undetermined. 

 Joblot says he believes there are three pairs. Schaeffer says 

 there are one or two pairs more. Muller describes five pairs 

 in Daphnia Pidex (pennata), but four only in longispina. All 

 the species however have five pairs. In the male, the first 

 pair of feet (plate ix. fig. 10.) differ considerably from the cor- 

 responding pair in the female. The appendix to the third 

 joint (a) (the fourth joint of Straus,) is terminated by a strong 

 claw, curved strongly outwards ; and the last bristle of the 

 third joint is much elongated, nearly the length of the body, 

 and floats outside the shell. Jurine describes this pair of 

 feet very particularly, and shows the use of them to be the 

 same as the hinge-joint antennae in the male Cyclops; viz. 

 for seizing and retaining hold of the female during the act of 

 copulation, the male introducing them along with the " har- 

 pons" or antenna, into the interior of the shell of the female, 

 and grasping her feet. 



Organs of Generation. — The male organs have never been 

 discovered, Muller having mistaken the antennae for them ; 

 neither have the female organs been observed, with the ex- 

 ception of the ovaries. That they reside in the lower portion 

 of the body appears most probable, from the description I 

 have already given of the method of copulation as observed 

 by Jurine. Straus thinks they have no external organs at 

 all, but that the male simply injects the semen under the 

 valves of the female, from which it introduces itself into the 

 ovaries. The ovaries are placed along the sides of the ab- 

 domen, as in Cyclops, and show their situation by the mat- 

 ter of the eggs in the shape of small round pellucid globules. 

 These make their appearance in the young insect after the 

 third moulting ; and gradually after that increase in size, lose 

 their transparency, become continuous, and form a dark mass 

 on the outer edge of the intestine, partly globular and partly 

 elongated. At the sixth segment of the body the ovary commu- 

 nicates with the open space on the back of the insect, already 



