no LECTURE VI. 



of the body, gradually diminishing in size; they are then reflected 

 forwards, as the ovaria, and form numerous, and apparently inextri- 

 cable coils about the two posterior thirds of the intestine. The vagina, 

 like the uterus, is lined by flat nucleated epithelial cells. 



In Cucullanus elegans and C. microcephalus the uterus is bifid, 

 but only one of the divisions is prolonged into the capillary ovarium : 

 the other horn terminates abruptly in a blind end. In Ascaris micro- 

 cephala Siebold found the uterus to divide into three horns, each 

 of which was produced into an ovarium: and in Filaria labiata 

 Nathusius saw the uterus divided into five tubes.* 



In the Nematoidea the male individual is always smaller, and 

 sometimes disproportionately so, than the female. At the season of 

 reproduction, the anal extremity of the male is usually bent round 

 the part of the body where opens the vulva of the female, to which it 

 attaches itself by the intromission of the single or double spiculum, and 

 by the adhesion of the surrounding tumid labia^ or of accessory dermal 

 appendages. As the vulva of the female is generally situated at a 

 distance from either extremity of her body, the male so attached has 

 sometimes the appearance of a branch or young individual sent ofi" 

 by gemmation at an acute angle to the body of the female. 



The evidence of the fertility of the compound cestoid Entozoa was 

 sufficiently marvellous. That which I have now to adduce, from a 

 calculation made by Dr. Eschricht in reference to the Ascaris lum- 

 bricoides, the commonest intestinal parasite of the human species, is 

 scarcely less surprising. The ova are arranged in the ovarian tubes 

 like the flowers of the plantago, around a central stem or rachis. 

 There are fifty in each circle ; that is to say, you might count fifty 

 ova in every transverse section of the tube. Now the thickness of 

 each ovum is 1-500 of a line, so that in the length of one line there 

 are 500 wreaths of fifty eggs each, or 25,000 eggs ! The length of 

 each ovarian tube is sixteen feet, or 2,304 lines, which, for the two 

 tubes, gives a length of 4,608 lines. The eggs, however, gradually 

 increase in size so as to attain the thickness of -^^ of a line ; we 

 therefore have, at the lower end of the tube, sixty wreaths of ova, or 

 3,000 ova in the extent of one line. The average number, through 

 the whole of the extraordinary extent of the tube, may be given at 

 1 4,000 ova in each line, which gives sixty-four millions of ova in the 

 mature female Ascaris lumbricoides ! 



The embryo is not developed within the body in this species : the 

 ova may be discharged by millions ; and most of them must, in largo 

 cities, be carried into streams of water. An extremely small pro- 



*XXIV. p. 151. 



