HYDKOZOA. 



The Hydra,* the history of which is so curious 

 and important, as to demand our special notice. 

 This little creature resembles a small portion of 

 green transparent thread, fastened by one end to 

 the stems of water-plants, 

 while the other is fur- 

 nished with several ra- 

 diating filaments of ex- 

 treme tenuity, which float 

 freely in all directions ; 

 should one of the nume- 

 rous water-fleas, or any 

 other minute animal, 

 come in contact with 

 these floating filaments, 

 though it touch but the 

 tip of one of them, it is 

 at once arrested in its 

 course, and in spite of 

 all its struggles dragged 

 to the central mouth, 

 which opens to receive 

 the helpless prey. 



The body of the Hydra 

 consists simply of a little 

 gelatinous bag, the mar- 

 gins of which are fur- 

 nished with filaments em- 

 ployed as tentacles, whilst 

 at the opposite end there 

 is a little sucker where- 

 by it fixes itself to foreign 

 objects. The microscope 

 reveals the substance of 

 these creatures to be composed entirely of a transpa- 

 rent glairy matter, in which granules of slightly 

 greater opacity may be observed to float. Not- 

 withstanding this simplicity of structure, however, 



* Hydra, a fabled monster that reproduced its heads as fast as 

 they were cut off. 



FlG. 17. LONG-ARMED HYDRA. 



