Till-: HYDRA. 21 



mouth is rarrounded with from five to • - 1 _rl 1 1 tentacli 

 feelers, which are hollow, the month opening into the i 

 tral cavity or stomach. The i lydra, attached to some leaf, 

 reaches its tentacles out in .-ill directions; a minute h - 

 or young snail or [nfusorian passing by will, if touched by 

 these feelers, be instantly paralyzed, and then the feelers 

 close over the helpless victim and ii is drawn into the stom- 

 ach and digested. This power of paralyzing and thus easily 

 capturing active living creatures i- due t" the presence in 

 the skin of the tentacles and body of what are called la 

 cells <>r nettling organs ( Fig. 20, c, d, > ). which are minute 

 cells containing a long barbed thread coiled up within the 

 ci'll. When the Eydra touches an animal Bwimming near 

 it, thousands of these little barbed cords are darted into 

 tlir victim, which is instantly paralyzed, and thus falls an 

 easy prey to its captor. These nettling organs are found 

 in all Ccelenterates, such as jelly-fishes ami coral polyps. 



Tito Hydra, like Borne other animals <>f simple structuri , 

 i.- capable to a wonderful degree of reproducing itself when 

 tut into pieces. Trembly, as early as 1741. nut only cut 

 Hydras in two, each pari becoming a perfect Hydra, hut 

 on slicing them across into thin rings he found that from 

 each ring grew out a crown of tentacles; lie splil them into 

 longitudinal strips, each portion becoming eventually a well- 

 shaped Hydra, and finally he turned some inside out. and 

 in a few days the Hydra .-wallowed and digested bits 

 meat, its former Btomach-lining having now become its 

 skin. The Hydra reproduces by budding as well as by 

 B :s. 



The process of budding is hut a modification of that in- 

 volved in natural self-division, and it is carried on to a 

 great extent in Hydra, a much larger number of individuals 

 being produced in this way than from eggs. Our figure 

 (IS) shows two individuals budding out from the parent 

 Hydra; the smaller hud (a) is a simple bulging out of the 

 body-walls, the hud enveloping a portion of the stomach, 

 until it becomes constricted anci drops off, the tentacles 



