THE FRESH-WATER HYDRA. 



83 



body of the prey like a sharp harpoon (Figs. 84, 85). If 

 you examine the spring closely, you will find that it is 

 only part of the cell, poked in like the finger of a glove 



Fig. 84. 



Thread-Cell, with its Theead uncoiled. 



turned inward, and when the tentacles, or feelers, 

 seize any thing, these glove-fingers all turn out . again. 

 Some of them are supposed to contain a poisonous juice, 



Fig. 85. 



Thread-Cell, with the Spring turned out like a Harpoon. 



which stuns or kills their prey in an instant. There is an 

 animal in the sea, the Portuguese Man-of-war, which 

 is really a dangerous creature, it has so many of these 

 sharp harpoons, which it throws at you if you touch it. 

 When the prey is benumbed or dead, the tentacles 

 carry it to the mouth, and it passes down into the long 

 tube, or body, of the hydra, where it is digested ; there 

 is no separate stomach, only one cavity, which runs all 



