370 ANIMAL PARASITES. 



3. The seminal cells. These are large, round bodies, which 

 present an extraordinary resemblance to the epithelium of higher 

 animals, and have even been taken for epithelium by Wedl. At 

 the same time they appear granulated. To the male sexual organs 

 belongs, lastly — ■ 



4. A sort of sucking-pit at the extremity of the abdomen, 

 which must serve as an auxiliary apparatus for the attachment of 

 the male, and as an assistance to the voluntary twisting of his 

 abdomen. In the textbooks we find nothing about this apparatus, 

 and yet it actually exists, although perhaps it assumes many 

 forms, in different positions of the worm. At the obtuse caudal 

 extremity of the male we see not unfrequently the whole 

 of the free margins projecting as light outlines, and from these 

 margins anteriorly and towards the tissue of the worm, a small, 

 cap or hood-shaped, hollow structure takes its rise, presenting the 

 complete form of a sucking disc engaged in action. Whether 

 this arrangement is produced by valvular seams or processes of 

 the integument, or, as it appears to me, by simple contraction of 

 the obtuse caudal extremity of the male, cannot be stated with 

 certainty. It is certain that it is possible for the obtuse tail to 

 acquire a sucker-like form, and that this assists the adhesion 

 of the male in coitu. At the same time I may remind the 

 reader of the valvular apparatus in the stomach. This apparatus 

 effects the complete prevention of the regurgitation of air and 

 nutritive material forwards, and thus renders the intestine a com- 

 pletely closed tube. This circumstance must of course assist the 

 action of the caudal extremity as a sucker. 



The females, whose comparative size varies according to the 

 state of maturity, are, under ail circumstances, larger than the 

 males. In the mature state they catch the naked eye, both by 

 their size and their white chalky colour, which is caused by our 

 seeing the pale, closely packed eggs shining out of the abundantly 

 filled uterus. The vaginal orifice lies on the same side as the 

 anal opening, and about as far behind the mouth as the 

 anus is distant from the caudal extremity, as is shown by the 

 measurements already given. It is situated before the middle 

 of the female, longish oval, and recognisable externally by no 

 remarkable fleshy protuberance. The tolerably long, slightly 

 twisted vagina is followed by the uterus, which, as well as the 

 ovary and Tuba Fallopii, is double in the Oxyurides. On the 

 simple vagina follows the uterus, one branch of which, the 



