THE FISHES, MOLLUSCA, AND OTHER OBJECTS. 55 



impossible for you to pull out an aquatic plant 

 without finding one, if not two species of that inte- 

 resting little zoophyte, the Hydra. As an object for 

 the aquarium it is unequalled, for there you may 

 more distinctly see it, and watch its daily life, which 

 is full of interest. Some of our readers may be 



Fig. 51. 



Second stage (magnified) iu development of Hydra. 



acquainted with the experiments of Trembly on this 

 creature, than which none ever more fully proved the 

 tenacity of its life. He found that by turning the 

 polyp inside out, as you would the finger of a glove, 

 no harm was done, but that the hydra seemed quite 

 as able to digest with its new stomach as with its 



