220 



THE ANIMAL PARASITES OF MAN 



forming a sphincter around the opening. Frequently also the 

 structure of the bladder extends to the tubules discharging into 

 it, which therefore are not to be regarded as separate " vessels," 

 but rather as tubular diverticula of the bladder, directed anteriorly. 

 In some few species the diverticula also branch and the branches 

 anastomose, so that a network of tubules ensues which receives the 

 vessels or capillaries. In such cases there are also ciliary tracts in 

 the tubules. 



The contents of the entire appar- 

 atus usually consist of a clear or some- 

 times reddish fluid ; in some species 

 there are larger or smaller granules, and 

 occasionally also concretions occur. 



g-P 



p.p. 



Ov. 



vag 



-ut. 



c.j. 



} Rec. ut. 



f.v.d. 



Rec. 



sem. 



nt. R. 



FIG. 126. Diagram of female genitalia. Ov., 

 ovary ; ovd., oviduct ; L.C., Laurer's canal ; 

 Rec. sem., receptaculum seminis ; Vit. R., vitel- 

 larian reservoir ; t.v.d., transverse vitelline duct ; 

 Oo., ootype ; Sh. gl., shell gland ; Rec. ut., 



FIG. 127. Diagram of male and part 

 of female genitalia. ut., uterus; vag., 

 vagina ; $ , opening of vagina ; g,s., geni- 

 tal sinus ; g.p., genital pore; <^, opening 

 of ejaculatory duct or vas deferens ; c.s., 

 cirrus sac ; c ., cirrus ; p.p., pars prostatica ; 



receptaculum uterinum ; ut., uterus. (The various s.v., seminal vesicle ; e.j., ejaculatory duct 



parts are not to the same scale.) (Stephens.] 



or vas deferens ; v.e., vas efferens ; t., testis. 

 (Stephens.) 



Sexual Organs. Nearly all the Trematodes are hermaphrodites, 

 and only a few (Schistosotnidce, Koellikeria) are sexually differen- 

 tiated. The sexual organs usually lie in the "central field" limited 

 by the gut caeca ; the vitellaria, on the other hand, are, as a rule, 

 external to the gut caeca in the " lateral fields." 



The male apparatus 1 is composed of two variously formed 

 testes (fig. 127) (globular, oval, indented, lobed, or ramified), which 

 may lie side by side or one behind the other ; from each testicle 

 a tube (vas efferens) originates ; sooner or later, both tubes as a rule 

 unite to form the ejaculatory duct or vas deferens, which is frequently 



The following description relates mainly to the Distomata. 



