352 ZOOPHYTES, 



SECTION II, 



Zoophytes, or Zoophytic.worms ; Polypes ; Corah ; and 

 Sponges. 



Zoophytes, or Plant-animals, are so denominated from their 

 existing in the shape of plants. Of these the genus Hydra, or 

 Polype, deserves our first attention ; not only from its wonderful 

 nature and properties, but because it serves as a kind of standard 

 or example of reference 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 pbaenomena similar to those recorded of the fabulous hydra 

 of antiquity, which, when one head is cut off, produced others in its 

 place. The character of the hydra, or polype, is a long, tubular 

 body, possessing a great power of contraction and extension ; 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 yel- 

 lowish-grey, and the green polypes, or the hydra fusca, grisea, and 

 viridis, of Linnaeus. 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 infe- 

 rior part will produce a new head and arms ; and this, in warm 

 weather, in the course of a very few days. If cut into three 

 pieces, the middle portion will produce both the head and tail ; 

 and in short, polypes may be cut in all directions, and will 

 still reproduce the deficient organs. The natural mode of pro- 

 pagation in this animal, is by shoots or offsets, in the manner of 

 a plant : one or more branches or shoots proceeding from the 

 parent stem, and dropping off when complete ; and it frequently 

 happens that these young branches will produce other branches 

 before they themselves drop off from the parent ; so that a 

 polype may be found with several of its descendants still adhering 



