274 PRACTICAL LESSONS IN SCIENCE. 



no difference about the kind ; locate a spider and commence ob- 

 servations on his habits and manners and customs at once, and 

 the work will afford you as much pleasure as any you ever did. 



The Scorpions have jointed bodies, with a hooked telson and 

 poison gland; they have a bilobed brain, and four pairs of lungs, 

 evidently the most highly developed of the arachnida. They 

 are more common in the warmer countries. The results of the 

 bite of the largest spiders, and the sting of the scorpion have 

 doubtless been much exaggerated, but enough is known to make 

 it wise to avoid the bite or sting when possible. 



The gossamer threads floating in great number in autumn 

 are the work of young spiders. Mounting some little elevation, 

 as a fence, in the warmer part of the day, they throw up the ab- 

 domen and allow the thread formed to float away on the ascend- 

 ing warm air until it becomes buoyant enough to carry the spi- 

 der away in the air. Spiders are oviparous, often carrying their 

 eggs on the abdomen until they are hatched. Spiders cast their 

 skin or moult several times before they attain full size. 



The Myriopoda are animals whose bodies are divided into 

 many segments, but without division into thorax and abdomen. 

 They have a distinct head, three pairs of jaws and numerous 

 pairs of legs. The head is much like that of insects, while their 

 form resembles that of worms. The black cylindrical many- 

 legged worm that rolls up into a ball is a myriopod. 



Some species of the centipede living in tropical countries at- 

 tain a large size, and the secretion from their poison gland is 

 dangerous even to man. 



