326 



THE ROUND WORMS 



:left 



americanus is also different, being terminally bipartite and deeply c 

 in the division of the dorsal ray, rather than tripartite and shallow, as 

 with A . duodenale. The anterior extremity of A ncylostoma bends in the 

 same direction as the general body curve while that of Necator hooks 

 back in an opposite direction to the body curve. In general, Ancylos- 

 toma is larger and thicker than Necator. 



. . . i . . . . I 



SCALE: 



FiG.76. la, Copulatory bursa of Nectar americanus, showing the deep cleft 

 dividing the branches of the dorsal ray and the bipartite tips of the branches; also 

 showing the fusion of the spicules to terminate in a single barb. Scale ^ mm - 

 ib, Branches of dorsal ray magnified. 2a, The buccal capsule of N. americanus. 

 2b, The same magnified. 3a. Copulatory of Ancylostoma duodenale, showing 

 shallow clefts between branches of the dorsal ray and the tridigitate terminations. 

 Spicules hair-like. 3b, The dorsal ray magnified. 4a, The buccal capsule of A. 

 duodenale, showing the much larger mouth opening and the prominent hook-like 

 ventral teeth. 4b, the same magnified. $a, Egg of N. americanus. sb, Egg of 

 A . duodenale. 6a, Rhabditif orm larva of Strongyloides as seen in fresh faeces. 6b, 

 Rhabditiform larva of hookworm in faeces eight to twelve hours after passage of 

 stool. 



The name hookworm was given to these nematodes from the hook-like processes 

 of the ribs of the rays of the copulatory bursa. Dubini called the Old World para- 

 site Agchylostoma, properly Ancylostoma, on account of the four formidable hook- or 

 claw-like ventral teeth of the buccal capsule. (<ryx^ 0<r , hook, and oro/xa, mouth.) 



A. ceylanicum is somewhat smaller than A. duodenale and in the copulatory bursa 

 of the male we have a deeper cleft in the dorsal ray and two rather long tips to each 



