THE NEMATODA. PARASITISM 



299 



The genital organs are of a type peculiar to the Nematoda. 

 They are paired in the female and unpaired in the male, 

 and lie free in the body cavity. The male apparatus is 

 composed of (a) the testis, a long coiled thread consisting 

 in its anterior part of a solid mass of immature sex-cells, 

 and in its hinder part'1'containing a cord or "rachis" in 

 the middle with riperVsex-cells attached to it, (0) the vas 



Fig. 206. — Muscle fibres of Ascaris. — From Parker 

 and Haswell, after Leuckart. 



A, A single fibre; B, several fibres in transverse section, 



with a portion of the ectoderm (below). 

 c, Contractile part of the fibre ; /, processes ; ««, nucleus ; 

 -Win ^, undiiferentiated protoplasmic part of the fibre. 



deferens of much the same width as the testis, (c) the vesicula 

 seminalis, a wider tube, (d) a short, narrow, muscular 

 ductus ejaculatorius. The spermatozoa are simple rounded 

 cells, which become amoeboid when they have been trans- 

 ferred to the female. The female organs correspond with 

 those of the male. The ovary has the same general struc- 

 ture as the testis, a hollow region which may be called the 

 oviduct connects it with the wide uterus, and the two uteri 



