THE HYDRA. 21 



mouth is surrounded with from five to eight tentacles or 

 feelers, which are hollow, the mouth opening into the cen- 

 tral cavity or stomach. The Hydra, attached to some leaf, 

 reaches its tentacles out in all directions; a minute insect 

 or young snail or Infusorian passing by will, if touched by 

 these feelers, be instantly paralyzed, and then the feelers 

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

 ach and digested. This power of paralyzing and thus easily 

 capturing active living creatures is due to the presence in 

 the skin of the tentacles and body of what are called lasso- 

 cells or nettling organs (Fig. 20, c, d, c), which are minute 

 cells containing a long barbed thread coiled uji within the 

 cell. When the Hydra touches an animal swimming near 

 it, thousands of these little barbed cords are darted into 

 the 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 and coral polyps. 



The Hydra, like some other animals of simple structure, 

 is capable to a wonderful degree of reproducing itself when 

 cut into pieces. Trembly, as early as 1744, not only cut 

 Hydras in two, each part becoming a perfect Hydra, but 

 on slicing them across into thin rings he found that from 

 each ring grew out a crown of tentacles; he split 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 swallowed and digested bits of 

 meat, its former stomach-lining having now become its 

 skin. The Hydra reproduces by budding as well as by 

 eggs. 



The process of budding is but 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 

 (18) shows two individuals budding out from the parent 

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

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

 until it becomes constricted and drops qS, the tentacles 



