ANIMAL PARASITES 



35 



opening, or vulva, about one-third the length of the worm from 

 the mouth, on the mid-ventral line. Passing in from this is the 

 short vagina, which soon divides into two long tubes which are 

 much convoluted and are filled with eggs. The portion of these 

 tubes nearest the vagina represents the uterus, the middle portion 

 is the oviduct, and the thinner distal portion the ovary. Enclosed 

 in the ovary is the long central rod, or rachis, around which the 

 eggs are arranged. 



Cuticula 

 SubcuticuUt 



Dorsal nerve cor& 



■Intestine 



Sfvjc/e /ibens 



Oviduct 

 Uterus 



'Zona mtiscle 

 celt 



Fig. 13. — Cross-section through the mid-body region of a female Ascaris mcyalo- 

 cephala. (After Kilkenthai.) 



Make a drawing showing the alimentary canal, the vagina, the 

 uterus, the oviducts, and the ovary. 



In a similar manner prepare a male specimen for study of the 

 internal anatomy. The male reproductive organs are situated 

 posteriorly. A long, single, much-coiled tube opens into the 

 cloaca, a short portion of the alimentary tract between the rectum 

 and anus. This tube is divided into three uneven portions: the 

 testis, the longest portion, which is a thin convoluted tube con- 

 taining a rachis with the sperm cells arranged around it similarly 

 to the condition in the female; the vas deferens, the part of this 

 tube not containing the rachis ; and the seminal vesicle, the central 

 portion, which is much shorter and thicker. The terminal por- 

 tion is again thinner and quite short, having a musculature of 

 its own. It serves as the ejaculatory duct. 



Compare the male and female worms carefully, but drawing of 

 male may be omitted. 



