THE CCELENTERATA 55 



derived from the seven-headed serpent of Greek 

 Mythology, the Hydra killed by Hercules, which 

 may be supposed to have presented a similar 

 straggling appearance. The diagram on page 36 

 represents a section through the middle of, the 

 body, only without the arms. 



Unlike the Sea-Anemone, the Hydra can walk 

 about. This it does in a very awkward manner, 

 much in the same way as the Caterpillar known 

 as the " Looper," clinging first with the front 

 and then with the back extremity of the body 

 (for head and tail they can hardly be called in so 

 simple an animal as the Hydra, although the 

 Looper caterpillar boasts both head and tail). 



The Hydra is so small an animal that it ap- 

 pears to the unaided eye merely as a tiny speck. 

 It may be found anywhere in British ponds and 

 ditches, standing on water-weeds. Like the Sea- 

 Anemone it preys on animals smaller than itself. 

 Nature has provided it with minute stinging 

 cells, which benumb its prey ; and in this all the 

 animals of the Ccelenterate group resemble it. 



One of the most curious things about the 

 Hydra is, that it often throws out buds. It can, 

 of course, produce eggs which are fertilized and 

 hatched in the usual way of eggs ; the buds are 

 an additional way of multiplying itself.* 



These buds are at first merely swellings, in 

 which both of the layers of the body join : they 

 grow larger ; become provided with tentacles and 

 a mouth, like the parent, and finally are cast off 

 as independent animals. 



* We may recall in comparison the way trees may be 

 propagated by slips independently of flowers producing the 

 seeds of the trees. 



