348 NATURAL HISTORY. 
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 by 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- 
laria, 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. 
Fig. 911:_Sertwlarian Polypes, There isan this respect an 
