58 
LIFE, IN ITS LOWER FORMS. 
CHAPTER VI. 
Polypifera {Polypes). 
Continued. 
Let us suppose that the buds continually put forth from 
the sides of the Hydra, instead of falling off to commence 
a new and isolated existence, remained permanently at- 
tached to the parent stock, giving forth in their turn buds, 
becoming permanent branches. We should then have the 
essential form of a Compound Polype ; such, for example, 
as that of the great marine family, Sertulariadce. Here 
we find the germ first developing a single Hydra-like 
polype, consisting of a slender stem or body of granular 
flesh, enclosing a stomachal cavity, the orifice of which is 
surrounded by a circle of sensitive tentacles. Soon, how- 
ever, a lateral bud projects, which shoots upward and 
develops a similar head of tentacles, while, from the 
side of this, another shoot still carries up the rising stem, 
which assumes a plant-like condition of branching stalks, 
with many lateral tentacled buds. It is true that in these 
marine species we commonly find an additional structure, 
of which no trace appears in the fresh- water Hydra. The 
whole compound animal is enclosed in a tube of trans- 
parent substance, somewhat flexible though firm, resem- 
