TYPE TRAC11EATA. 479 



they are the modified nephridia of the third segment of the 

 body, that which bears the oral papillae, and furthermore it is 

 to be noted that in the last or next to last (according to the 

 species) limb-bearing segment, in which nephridia are wanting, 

 are found the ducts of the reproductive organs a fact which 

 suggests that these are also modified nephridia. This idea is 

 confirmed by the development of the genital ducts, and car- 

 ries with it the corollary that the cavities of the reproductive 

 organs (Fig. 220, g) are portions of the crelom, just as they 

 were shown to be in the Mollusca (see p. 288). 



In addition to the nephridia there are associated with cer- 

 tain of the appendages glands which open on the under sur- 

 face of their basal moiety and are termed the crural glands. 

 In P. capensis they are present in all the appendages except 

 the more anterior one, and the slime-glands are simply the 

 highly-modified crural glands of the oral papillae, those of 

 the last pair of appendages in the males of this species being 

 similarly elongated though possessing a different function. 

 In P. Edwardsii, however, crural glands occur only in the 

 males, and in these only in a few segments immediately in 

 front of that bearing the reproductive opening. 



The Protracheata are bisexual, the female usually being 

 somewhat larger than the male. The ovaries are paired, 

 though included within a common capsule, and lie in the pos- 

 terior part of the coelom. They are continuous with two 

 nteri, which immediately at their origin are united by a trans- 

 verse tube, and each bears a receptaculum ovorum and a 

 receptaculum seminis. Beyond this each continues its course 

 along the side of the body, passing backwards to finally 

 unite at the common orifice, lying a short distance in front of 

 the anus on the ventral surface of the body. The testes are 

 slender paired structures which are continuous with a slender 

 vas deferens. This dilates a short distance from the testis 

 into a vesicula seminalis and then unites with its fellow of the 

 opposite side to form a slender somewhat coiled tube, the 

 ductus ejaculatorius, in the terminal portion of which the 

 spermatozoa are united together into a spermatophore. The 

 Protracheata are viviparous. 



