i 7 8 



THE ANIMAL PARASITES OF MAN 



larger spines. The oral sucker is a little larger than the peduncu- 

 lated ventral sucker (0*07 and 0*059 mm - respectively). The anterior 



part of the body measures from 0*2 

 0*3 mm. in length ; the oesophagus 

 is as in the male. The intestinal bi- 

 furcation is in front of the ventral 

 sucker, the 'two branches uniting behind 

 the ovarium and the trunk running in 

 a zig-zag manner to the posterior bor- 

 der. There are indications of blind 

 ducts at the flexures. The ovary is 

 in a median position. In young females 

 it is of an elongated oval shape ; in 

 older females the posterior end becomes 

 club-shaped, whereas the anterior end 

 becomes attenuated ; the oviduct origi- 

 nates at the posterior end, but imme- 

 diately turns towards the front and 

 joins the parallel vitellaria in front 

 of the ovary (fig. 112), where the 

 shell gland cells discharge ; the common 

 canal becomes dilated to form the ootype, 

 and then proceeds as the uterus along the 

 central field to the genital pore, which lies 

 in the middle line immediately behind 

 the ventral sucker. The single vitelline 

 sac starts behind the ovary and ex- 

 tends to the posterior end. The acini 

 are situated at the side of the excretory 

 duct, which runs a median course. The 

 eggs are fusiform, much dilated in the 

 middle ; they have no lid, and are 

 provided with a terminal spine (rudi- 

 mentary filament) at the posterior end 

 measuring 0*12 O'lg mm. in length and 

 0-05 0-073 mm. in breadth (fig. 113). 

 Eggs retained in the body of the host 

 carry the thorn-like appendix in the 



vicinity of the posterior border but laterally. 



[The eggs are yellowish in colour, slightly transparent and 



provided with a thin shell. The spine may sometimes be absent. 



The eggs apparently vary a great deal in size. F. V. T.] 



FIG. no. Transverse section 

 through a pair of Schistosomum. 

 In the male the point of reunion 

 of the intestinal forks has been 

 cut across. (After Leuckart.) 



O.s. 



Oe. 



Pi Oe. 



_ V.S, 



G f p. 



T r 



FIG. in. Anterior end of the 

 male Schistosomum h&matobium 

 (Bilh.). 40/1. V.s., ventral 

 sucker ; /., intestinal branches; 

 G.p., genital pore ; T., testes ; 

 O.5., oral sucker ; Oe., oeso- 

 phagus with glandular cells ; 

 V.s., vesicula seminalis. (After 

 Looss.) 



