SOME LOWER ANIMALS 251 



thousand-legs. This, however, has two pairs of legs upon 

 each segment. It feeds chiefly upon decaying vegetable 

 matter. It is more cylindrical in shape than the centipede, 

 and is harmless. 



In the cellar among the vegetables, under boards and 

 stones, we often find little flattened, jointed, insect-like animals 

 which have legs on all the body segments, and which have the 

 habit of curling up into a rounded mass when disturbed. 

 These are called Pill-bugs, or Wood-lice, but are related more 

 closely to the crayfish than to insects. 



It is well also to call attention to the many minute forms of 

 animals that swarm in the stagnant waters of pools and 

 sluggish streams, and in lakes. A jar containing such water 

 will show to the naked eye even these animalcula swimming 

 about, some barely visible, others large enough to be plainly 

 seen. Many of these consist of water-fleas and copepods, 

 animals related to the crayfish. With a compound micros- 

 cope a drop of water is seen to teem with animalcula. Let 

 the children know that these small animals are very important, 

 in that they form the food of many larger aquatic animals. 

 Fish are very fond of them. Put some minnows in a jar with 

 these animalcula, and see how eagerly they feed upon them. 



The seashore is a rich field for the naturalist, and teachers 

 on the coast should make the most of their opportunity by 

 studying the plants and animals which the waves throw upon 

 the sands. In inland waters, though the life is not so varied, 

 yet there are some animals that we should study. 



The Crayfish is very common in lakes and streams. Its 

 structure should be compared with that of the insects. The 

 articulated body and appendages should be noted. Study 

 the eyes, mouth-parts, the large claws and feet, the swim- 



