348 NATUEAL HISTOET. 



604. But the most remarkable fact in regard to the 

 Hydra is, that if a small piece of its body, or even if a 

 tentacle be torn off", the separated part will itself become 

 a perfect animal. Thirty or forty Hydras may be pro- 

 duced by cutting a single one into pieces. The Hydra 

 of ancient fable seems thus to be realized in nature. The 

 Hydra does not seem to suffer at all from mutilation, but 

 young Polypes sprout abundantly from any wound that 

 may be made. Two Polypes may even be grafted to- 

 gether \)y their cut surfaces. This can be done not only 

 with those of the same species, but with different species, 

 as the green and brown Hydras. 



605. There are some Polypes, belonging to the same 

 order with the Hydras, which have a much stronger re- 

 semblance to plants in their habits and arrangements. 



They are situated on horny 

 stalks, and, in some cases, 

 these stalks have branch- 

 es, with cells on them, for 

 containing the little Pol- 

 ypes, as seen in the Sertu- 

 1 aria. Fig. 271. The stalk 

 and branches here are hol- 

 low, being lined with a 

 membrane which is the 

 essential part of the ani- 

 mal, or, rather, of the com- 

 munity of animals thus 

 united together. Each in- 

 dividual Polype may be 

 considered as having a 

 stomach of its own, but 

 communicating with 

 a sort of stomach common 

 to them all, which lines 

 the branches and the stalk. 

 Pig. 2T1.— Sertuiarian Polypes. There is in this respect an 



