BRANCH HERMES: THE WORMS 



141 



it is sometimes said that these worms come down with the 

 rain. They have in reality come from the bodies of insects 

 in which they pass their young or larval stages as parasites. 

 The hair-worms all live as parasites during their larval 

 stage, and as free independent animals in their adult stage. 

 Some of them require two distinct hosts for the comple- 

 tion of their larval life, living for a while in the body of 



one, and later in the body of 

 another. The first host is 

 usually a kind of insect which is 

 eaten by the second host. The 

 eggs are deposited by the free 

 adult female in slender strings 

 twisted around the stems of 

 water-plants. The young hair- 

 worm on hatching sinks to the 

 bottom of the pond, where it 

 moves about hunting for a host 

 in which to take up its abode. 



The terrible TricJiina spiralis 

 (fig- 33)' which produces the 

 disease called trichinosis, is 

 another roundworm of which 

 much is heard. This is a very 

 small worm which in its adult 

 condition lives in the intestine 

 of man as well as in the pig and 

 other mammals. The young, 

 which are borne alive, burrow 

 through the walls of the intes- 

 tine, and are either carried by the blood, or force their 

 way, all over the body, lodging usually in muscles. 

 Here they form for themselves little cells or cysts in 

 which they lie. The forming of these thousands of tiny 

 cysts injures the muscles and causes great pain, sometimes 



FIG. 33. Trichina spiralis, en- 

 cysted in muscle of a pig. 

 (From specimen.) 



