PHYSIOLOGY OF THE INVERTEBRATA. 443 



canals, called vaginae by Zenker, each of which is continued 

 into a long convoluted transparent tube, and eventually ter- 

 minates in a large vesicle, the spermatheca, in which the 

 spermatozoa of the male are received. In the males, the 

 antennae, the second maxUlse, or some of the thoracic limbs, 

 are modified in such a manner as to enable them to seize and 

 hold the females. The testes are elongated caeca in Cypris, 

 globular vesicles in Cythere, and communicate with a long 

 vas deferens, which opens into the copulatory apparatus." 

 (Huxley.) The development of Cypris (taken as a type of 

 the Ostracoda) consists of a complicated metamorphosis, but 

 begins, with a Nauplius larva, which is furnished with a 

 bivalve shell. 



In the BrancMopoda the sexes are distinct, and sexual 

 reproduction Occurs ; but in Apus, Daphnia, and other 

 genera, parthenogenesis occurs, along with sexual reproduc- 

 tion. In Limnadia gigas no males are known to exist. 



The Cirripedia are, as a rule, hermaphrodites. The ovaries 

 are situated in the peduncle ; and the oviducts pass into the 

 body and open on the basal joint of the first pair of cirri. 

 The testis consists of numerous ramified follicles, which are 

 united to two long vasa deferentia; the latter unite, and 

 then pass into the penis. The penis is situated in, and opens 

 at, the extremity of the tail. The tail can be used as a 

 copulatory organ, being brought into contact with the aper- 

 ture of the oviducts. Self-impregnation may take place in 

 the Cirripedia. It was Goodsir* who first proved that all 

 these animals were not hermaphrodites, for in Balanus 

 lalcenoides the sexes are distinct. Darwin f proved that 

 Scalpelhim and lUa are both dioecious and hermaphrodite 

 Cirripedia. The males of lUa lie within the sac of the 

 female ; as these males are supernumeraries, Darwin termed 

 them complemental males. 



After impregnation the segmentation of the vitellus is 



* Edinburgh New Philosophical Journal, 1843. 

 f Nature, 1873, p. 431. 



