HYDRA. 353 



they are frequently liberated by the opportune break of 

 the worm, when each obtains his share ; but should the 

 prey prove too tough, woe to the unready! the more 

 resolute dilates the mouth to the requisite extent, and 

 deliberately swallows his opponent ; sometimes partially, 

 so as, however, to compel the discharge of the bait ; while 

 at other times the entire polype is engulfed ! But a polype 

 is no fitting food for a polype, and his capacity of endurance 

 saves him from this living tomb ; for, after a time, when 

 the worm is sucked out of him, the sufferer is disgorged 

 with no other loss than his dinner." 



The organ of prehension, which is called the hasta, con- 

 sists of a sac opening at the surface of the tentacle, within 

 which, at the lower portion, is placed a saucer-shaped 

 vesicle, supporting a minute ovate body, which again bears 

 a sharp calcareous piece called the sagitta, arrow. This 

 can be pushed out at the pleasure of the animal, serving 

 to roughen the surface of the tentacle, and afford a much 

 firmer hold of its living prey. The polype increases 

 rapidly : a portion of the body swells, a young one puts 

 forth its head from the part, its arms begin to grow, it 

 then is industrious in catching food ; its body, communi- 

 cating with that of its parent and participating in the 

 fears and actions of its progenitor, is finally cast off to 

 wander the world of waters. Sometimes, ere yet free from 

 parental attachment, it has two generations on its own 

 body. Four or five offspring are thus produced weekly. 

 But the most extraordinary circumstance in respect to this 

 creature is thus described by M. Trembley : " If one of 

 them be cut in two, the fore party which contains the head 

 and mouth and arms, lengthens itself, creeps, and eats on 

 the same day. The tail part forms a head and mouth at 

 the wounded end, and shoots forth arms more or less 

 speedily, as the heat is favourable. If the polype be cut 

 the long way through the head, stomach, and body, each 

 part is half a pipe, with half a head, half a mouth, and 

 some of the arms at one of its ends. The edges of these 

 half pipes gradually round themselves and unite, beginning 

 at the tail end ; and the half mouth and half stomach of 

 each becomes complete. A polype has been cut lengthways 

 at seven in the morning, and in eight hours afterwards 



A A 



