196 LECTURE XII. 



ence in many other genera of zoophytes more or 

 less allied to it. 



The genus Hydra or Polype, comprehending 

 the real or fresh- water polypes, was so named by 

 Linnaeus because in reality it affords phenomena 

 similar to those recorded of the fabulous Hydra of 

 antiquity, which, when one head was cut off, pro- 

 duced others in its place. The character of the 

 Hydra or Polype is a long, tubular body, possessing 

 a great power of contraction and extension - 9 affix- 

 ing itself by the tail ; and furnished at its upper 

 or open end with a certain number of long arms 

 or tentacula, differing in number in the different 

 species. The principal species- are the brown, the 

 yellowish-grey, and the green Polypes, or the Hy- 

 dra fusca, grisea, and viridis of Linnseus. These 

 curious animals may be found in small streams 

 and in stagnant waters, adhering to the stems of 

 aquatic plants, or to the under surfaces of the 

 leaves, and other objects. They prey on small 

 worms, Monoculi, and many other animals which 

 happen to occur in the same waters. If a Polype 

 be cut in two, the superior part will produce a 

 new tail, and the inferior part will produce a new 

 head and arms ; and this, in warm weather, in the 



