ROUNDWORMS— THE NEMATHELMINTHES 



165 



of life that do not have chlorophyll must depend upon other forms of life 

 for their food supply. Hence, the parasites are distinguished from the 

 others merely by the fact that they derive their nourishment from others 

 while the organisms furnishing the nourishment are still living. The 



Photos by Winchester 



Fig. 11.7. Variation in the eggs of parasites. Because of the structural differences 

 in the eggs it is possible for a parasitologist to determine the kind of parasites in an 

 animal's body by examination of the eggs in the feces or other body excrements. A. 

 Dog tapeworm, Dipylidium caninum. B. Goat lung worm. C. Dog hookworm. D. 

 Dog tapeworm, Taenia pisiformis. E. Sheep thorn-head worm. F. Dog ascaris. 



fact that they cause injury, disease, and sometimes death to the host which 

 furnishes the nourishment is an unfortunate incident accompanying the 

 habits of the parasite. So far as the parasite is concerned, it would be 

 better if the host remained in the best of health, for in this way the parasite 



