260 GENERAL ZOOLOGY 



Department of Agriculture in Washington discovered that 

 carbon tetrachloride is a much more effective cure for hook- 

 worm patients than any drug previously used. 



Hair Snakes. A myth believed at least for a time by most 

 children in rural communities maintains that hair from a 

 horse's tail, if allowed to stand in water, turns into a hair 

 snake or hairworm. Many people think they have carried 

 on a scientific experiment when they put a hair into a water- 

 ing trough, and later find there a living, wriggling creature 

 very much like a hair in appearance. The performer of such 

 an experiment may not be aware that in the meantime a 

 grasshopper or a cricket has fallen into the watering trough 

 and from its body has crawled the long hair-like worm. The 

 Gor'dius, or hair snake, lives, as an adult, free in watering 

 troughs and streams. The female deposits long strings of 

 eggs, which hatch into microscopic larvae, each provided 

 with a peculiar boring spine. By use of this spine the larva 

 drills its way through the body wall of a cricket or a grass- 

 hopper and comes to lie in the body cavity. Here it com- 

 pletes its growth but is not able to reproduce unless the 

 insect bearing it gets into water. Then the " snake " emerges 

 ready to continue life as a free individual. 



Definition of Nemathelminthes. All the roundworms whose 

 bodies are not segmented but contain a body cavity belong 

 to the phylum Nemathelmin'thes (Gr. nema, "thread"; 

 helmins, "worm"). 



The roundworms include some of the most important 

 enemies of man. As parasites they destroy his domestic 

 animals and crops and many attack man directly. They 

 produce disease and in some localities reduce the inhabit- 

 ants to the lowest physical and economic standards of ex- 

 istence. Knowledge of these worms has been scanty until 

 recently. 



