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TEXTBOOK OF ZOOLOGY 





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Fig. 395.-^Life history of hookworms from egg to infective larva. 1, &^^ of 

 Necator aniericanus at time of leaving host; 2, same of Ancylostoma duodenale; 

 3 to 7, segmentation and development of embryo in egg ; 8, newly hatched embryo ; 

 9, same of Strongyloides for comparison (note length of oral cavity and size of 

 genital rudiment, </.?•.) ; 10, second stage larva; 11, fully developed lai'va ; an., anus; 

 ex. p., excretory pore ; g.r., genital rudiment ; int., intestine ; n.r., nerve ring ; oes., 

 esophagus; oes.b.. esophageal bulb; or. cav., oral cavity; sh., sheath. (After Looss 

 from Chandler, Hookioorm Disease. Reprinted by permission froiu Introduction 

 to Hunia/n Parasitology by Chandler, published by John Wiley and Sons, Inc.) 



