FROM A POXD, AXD THEIR TENANTS. 167 



The Hydra is a sensitive creature, as anyone can prove by 

 touching it, and the purpose of this sensitiveness is easily dis- 

 covered, for when a water-flea touches its outspread feelers, or 

 tentacles, these organs will be observed to at once twine them- 

 selves round its body, and, after overcoming the victim, convey it 

 to its mouth, down which it is rapidly drawn into the stomach. 

 But what strikes us as the most remarkable is the suddenness 

 with which the victim is rendered helpless ; for so quickly do its 

 struggles cease that we might well imagine it to have become 

 paralysed. 



When, however, we place a tentacle of the Hydra in a live-box 

 under our microscope and gently press it, we discover the cause, 

 for we observe numerous little thread-like darts shoot out from 

 sundry cells embedded in the tissues, and from the way in which 

 these cells burst on being irritated, we are at once led to the con- 

 clusion that each cell is a sort of poison apparatus, capable of 

 paralysing the unfortunate victim into whose body the darts 

 penetrate.* 



But the most wonderful part of the history of the Hydra is 

 that it can be cut in pieces, and each piece will grow into a 

 l^erfect creature ; while even if turned inside out like the finger of 

 a glove, this strange animal suffers no apparent inconvenience, for 

 it will eat and digest its food the same as if left in its normal 

 condition. 



The ordinary, and indeed natural, ways of increase in Hydra 

 life are two : one by means of budding and the other by means of 

 eggs. The former appears to be the method of increase during 

 the summer and warmer months, and the latter during those 

 colder periods of the year so fatal to the lower forms of animal 

 hfe. Indeed, it is not uncommon to see a hydra with a young 

 one growing from its side, which in its turn has budded and pro- 

 duced a miniature of itself, thus presenting three generations 

 adhering together as a compound organism. Sooner or later, 

 however, the young hydra — hke precocious offspring — sever their 

 connection with the parent body, and float away through the 



* This is not established. The writer does not notice the fine thread; 

 which attach each dart to the body. — Ed. 



