THE /IMCEBA, HYDRA, AND OTHER SIMPLE ANIMALS 123 



water and observe Hydra's method of catching and eating 

 food. Note that when it captures one of the water-fleas 

 with its tentacles the flea soon ceases to struggle. It is 

 paralyzed. On the tentacles are many extremely fine, 

 little, stinging threads, which lie coiled up in small pockets 

 until prey is captured, when they uncoil, shoot out, and 

 sting. If Hydra catches an animal too large to be 

 crowded into its mouth it releases it. 



Note that Hydra can contract its tentacles and its whole 

 body until it looks like a small egg with a rosette of short 

 blunt fingers at one end (fig. 85). Sometimes Hydra 

 may be seen with another much smaller one growing out 

 from it. This is a new one, forming by the process of 

 "budding." It will grow and develop until about as 

 large as the parent, when it will break off, and attaching 

 itself elsewhere will begin an independent existence. 

 Hydra has the interesting power of being able to regen- 

 erate itself if cut in two. In such a case each half will 

 usually develop into a new complete Hydra. 



Hydra belongs to the branch of animals called Ccclcn- 

 terata, which includes also the sea-anemones, corals, and 

 jellyfishes (see next chapter). 



For detailed accounts of the structure and life-history 

 of Amoeba, Paramcecium, Vorticella, other Protozoa, and 

 Hydra, see Parker's " Lessons in Elementary Biology." 



