THE HYDRA, 
31 
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« 
achand 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, d, e), which are minute 
cells containing a long barbed thread coiled up 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 Coelenterates, 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 {a) is a simple bulging out of the 
body-walls, the bud enveloping a portion of the stomach, 
until it becomes constricted and drops off, the tentacles 
