PHYSIOLOGY OF THE INVERTEBRATA. 443 



canals, called vagina3 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 

 antenna?, the second maxillae, or some of the thoracic limbs, 

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

 hold the females. The testes are elongated casca in Ciji^ris, 

 globular vesicles in CytJicrc, and communicate with a long 

 vas deferens, which opens into the copulatory apparatus." 

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

 the Ostvcwoda) consists of a complicated metamorphosis, but 

 begins with a Nauplius larva, which is furnished with a 

 bivalve shell. 



In the Branchiopoda the sexes are distinct, and sexual 

 reproduction occurs; but in Ajms, Ucq^/utio, and other 

 genera, parthenogenesis occurs, along with sexual reprodvic- 

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



The Cirripcdia 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 Cirripcdia. It was Goodsir* who first proved that all 

 these animals were not hermaphrodites, for in Bahama 

 hala'noides the sexes are distinct. Darwin t proved that 

 SfaljJcllum and Ibla are both dioecious and hermaphrodite 

 Cirripedia, The males of Ibla 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 



* Edinhuryh New Philosophical Journal, 1843. 

 t Nature, 1873, p. 431. 



