88 NATURAL HISTORY OF ARTHROPODS. 



by a dog, wolf, or other carnivore, these sexless forms pass to the nasal region, and 

 there gradually acquire the sexual condition, develop their young, which pass out with 

 the nasal mucus, and fall upon the grass, or other food of the rodents. These young 

 may then be eaten by the rabbit, and in his body they develop by a series of changes, 

 pass through the walls of the intestine to the lungs or liver, where they become 

 encysted, ready to go through the same cycle of changes as did their parents. Thus, 

 like the tape-worms, two distinct hosts are necessary to complete the circle of life. 

 Other forms occur in serpents, apes, etc., and even in man, but their life-history has 

 not been traced with the completeness of .that of Pentastomum tcenioides detailed 



above. 



J. S. KINGSLEY. 



FIGS. 122 and 123. Agnostus nudus, trilobite, larva and adult. 



