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, resetn- 



