NEMATHELMINTHES 



89 



.^\ 



Excretory Pore 



Pharynx 



-Excretory Tube 



Oenito/ Pore 



— t/agino 



% 



^--Uterus 



-^4 — Ovary 



Eggs of the pig ascarls did not produce mature ascarids in the mon- 

 key and the two human subjects. No intermediate host is required 

 for the development of Ascaris hwibricoides. 



Anatomy.— TVq female Ascaris lumbricoides is about six inches 

 long. It has a slender body tapering 

 at both ends. The body is grayish 

 pink in color with lateral stripes. 



Digestive Syste?n. — The month has 

 one dorsal and two sub-ventral lips. 

 The dorsal lip bears two large papillae, 

 each sub-ventral lip bears a small 

 lateral papilla and a large sub-ventral 

 papilla. The amphids are small pores 

 slightly dorsal to the lateral papilla. 

 Amphids are supposed to be gustatory. 

 The long muscular esophagus leads into 

 the intestine which runs throughout 

 the body, ending with a slightly smaller 

 rectum that opens at the anus. Ab- 

 sorption takes place through the walls 

 of the intestine. 



Excretory System. — The excretory 

 system consists of two longitudinal 

 canals, one in each lateral chord; they 

 open to the exterior through a single 

 ventral pore near the post-pharyngeal 

 region. (Figure '^i^d) 



Reproductive System. — The female 

 reproductive system consists of two 

 slender coiled, thread-like ovaries, con- 

 tinuing into the dilated uteri which join 

 to form a short tube, the vagina. The 

 sperm from the male fertilizes the eggs 

 in the uteri and the eggs pass out 

 through the genital pore, situated about 

 one-third the distance from the head, 

 a shell resisting digestive juices. The male (about 4 inches long) 

 has a sinale thread-like testis from which the vas deferens leads 

 to the seminal vesicle and thence to the ejaculatory duct which 

 opens at the rectum. 



--Intestine 



-Excretory Tub^ 



Fig. 36. Anatomy of a female 

 round worm Ascaris. (After 

 Shipley and McBride. Courtesy 

 of Macmillan and Co., Ltd.) 



The eggs are covered with 



