HTDE^. 301 



apparently disappear about autumn, but reappear again in the 

 spring from the OTa which during the previous summer had been 

 deposited at the bottom of the aquarium. According to Mr. 

 Fullagar "the reproduction of Hydra vulgaris from ova takes 

 place in the autumn, and that of Hydra viridis in the spring." 



There is another way by which Hydrse may be increased, 

 besides being produced from eggs and by budding, and this is 

 by artificial division. This extraordinary power on the part 

 of this polype has given it the generic name of Hydra, and weU 

 is it deserved, for it does seem to rival in this particular that 

 monster which, according to the ancients, was conquered 

 by Hercules. If a Hydra is cut in half, it apparently suffers 

 little or no pain ; for the half containing the tentacles wiU sink 

 to the bottom of the water, because it has no disc by which 

 it can adhere, but will, if it has an opportunity, immediately 

 seize and devour prey. The other half will remain cliuging 

 to the spot to which it was affixed when the operation took place, 

 and gradually develop a new mouth and new tentacles. Should 

 a polype be divided into four or more pieces, it wiU, in all pro- 

 bability, produce in time the same number of perfect Hydra3; 

 or, if it be slit from top to bottom, the cut portions of each 

 piece will slowly unite, and two Hydrse wiU take the place of the 

 original one. It has been said that a fresh polype will grow 

 from a small portion of a tentacle, but this is very doubtful. 

 It has been generally noticed that those Hydras which have been 

 the result of artificial division are stronger and finer animals 

 than those which have sprung from eggs or have been produced 

 by germination. M. Trembley has recorded that he was suc- 

 cessful in turning some of these polypes inside out, and that 

 even tinder this unnatural condition they were able and willing 

 to capture their prey and feed upon it and thrive. 



Anyone who carefully studies these wonderful fresh-water 

 Hydrse will be sure to be amply rewarded for his trouble, for 

 nothing can be more extraordinary than their habits and life- 

 history. 



