74 WONDERS OF ORGANIC LIFE. 



which immediately affects it. Here, perhaps, 

 by way of rendering the matter clear to our 

 readers, the author may be permitted to quote 

 from his own writing, making such omissions 

 and alterations as are necessary for brevity's 

 sake. " In order to convey an idea of these 

 polype-bearing animals, let us begin with the 

 simplest of their forms. There is in fresh- 

 water ponds or slow rivers, a minute gelatinous 

 creature termed hydra, of which several species 

 are known. These animals are of slender 

 figure, with an internal cavity, and a mouth 

 surrounded by movable arms or tentacles ; 

 they possess the most extraordinary powers of 

 elongation and contraction, and are highly car- 

 nivorous ; they attach themselves, by means of 

 a caudal sucker, to the leaves of aquatic plants, 

 and spread abroad their arms in quest of prey, 

 which they drag to the mouth and engulp. 

 No nerves or muscular fibres have been de- 

 tected, but the gelatine composing the body is 

 replete with minute granules. The hydra is 

 tenacious of life, and when cut asunder each 

 part becomes a perfect and independent being. 

 Yet, though apparently insensible to pain, the 

 hydra appears to appreciate the presence of 

 light, and its tentacles doubtless feel the prey 

 around which they cling. The hydra is free, 

 and moves about over the surface of the leaves, 

 or swims in the water with the tentacles down- 

 wards, the caudal sucker acting as a float. 

 When alarmed, it contracts its tentacles, and 

 shrinks into the form of a small globule, easily 



