POLYPES. 217 



bottle upon which the light falls, and will be seen 

 floating about in that quarter of the flask, or 

 adhering to that portion which is turned towards 

 the window of the apartment. With a magnifying- 

 glass it is easy to recognize Hydra fusca, which is 

 brown or olive coloured, and H. viridis, which is 

 green. Sometimes a reddish-brown variety (H. 

 rubra) will be also seen. The little creatures 

 appear like very small floating sacks, having four 

 arms or tentacles spreading out from the orifice of 

 the sack. If these animals be cut into several 

 pieces with a scissors, each piece becomes a new 

 hydra; if one of them be turned inside out like a 

 glove, it lives so, the external part, which is now 

 the interior, carries on the process of digestion as 

 if it had always been inside. 



Polypes are reproduced by " budding," by spon- 

 taneous division, or by eggs. In the first process 

 one or more buds form around the mouth (orifice of 

 the sack), or on some other part of the animal's body. 

 This bud, which at first appears as a little globule, 

 gradually developes itself into a complete polype, 

 and drops off. This process of reproduction is ex- 

 tremely rapid ; a single day often suffices for several 

 successive generations to make their appearance. 

 Thus, a child polype born by budding at six o'clock 

 in the morning, will, in many cases, be a grand- 

 father by six in the afternoon. But this rapid sue- 



