138 THE ANIMAL PARASITES OF MAN 



which opens close to the genital orifice, or more rarely discharges 

 direct into the genital pore and enters the muscular CIRRUS 

 POUCH ; the cirrus itself, after being exerted, may be projected, 

 and serves as an organ of copulation. In the atrium, and as a 

 rule enclosed in the cirrus pouch, is found a mass of one-celled 

 glands (prostata) as well as a vesicula seminalis (which is likewise 

 within, or may also be outside the pouch). 



The female genitals (fig. 73) consist of an ovary usually situated 

 in front of the testes, the form of which varies according to the 

 species, the usual pair of vitelline sacs, the conducting passages and 

 a number of auxiliary organs ; the short oviduct directed towards 

 the centre starts from the ovarium, and is connected at the 

 median line with the excretory ducts of the vitelline glands. These 

 grape-like glands possess longitudinal excretory ducts, which assume 

 an oblique direction behind the ovary, unite together at the median 

 line and form one single tube, often carrying a vitelline reservoir 

 that unites with the oviduct. At this spot, moreover, there 

 frequently occurs a canal (Laurer's canal) which originates on the 

 dorsal surface, and to the inner end of which a vesicle filled 

 with sperm (receptaculum seminis) is usually suspended. More- 

 over, there are also numerous radial one-celled glands (shell glands) 

 at the place where the oviducts, vitelloducts and Laurer's canal 

 are united. In this region (ootype), which is usually distended, 

 the germ cells are fertilised, surrounded with vitellus and shell 

 material, and as ova with shells they pass direct to the uterus, 

 which, with its many convolutions, occupies a larger or smaller 

 portion of the central field, but the terminal part of which lies 

 next the cirrus pouch and discharges beside the male orifice either 

 to the surface of the body or into a genital atrium. The terminal 

 portion of the uterus, which is often of a particular formation, 

 serves as a vulva (METRATERM). 



The orifice of the sexual organs is generally situated at or 

 near to the median line on the ventral surface and in the anterior 

 region of the body ; in the Fasciolidea it is frequently in front of 

 the ventral sucker, in other families at a suitable spot in the 

 vicinity of the intestinal bifurcation. 1 



1 The typical position of the genitals is subject to many deviations, which are of 

 importance in the differentiation of the species and families. The following lines 

 give some few of these deviations : ( i ) The genital pore remains on the ventral sur- 

 face, but is situated next to or behind the abdominal sucker, or it becomes marginal, 

 and is then found in front of or next to the oral sucker or at a lateral edge, or, 

 finally, in the centre of the posterior border ; the conducting passages also 



