USE OF THE MICROSCOPE IN ZOOLOGY, 53 



seem to depend are cut away, they are reproduced, 

 and the lopped-off parts remain not long without a 

 new body. If only two or three tentacula are em- 

 braced in the section, the result is the same, and a 

 single tentaculum will serve for the evolution of a 

 complete creature. When a piece is cut out of the 

 body, the wound speedily heals, and as if excited by 

 the stimulus of the knife, young polypes sprout from 

 the wound more abundantly, and in preference to 

 unscarred parts ; when a polype is introduced by the 

 tail into another's body, the two unite and form one 

 individual ; and when a head is lopped off, it may 

 safely be engrafted on the body of any other which 

 may chance to want one. You may slit the animal 

 up, and lay it out flat like a membrane with impunity ; 

 nay, it may be turned inside out, so that the stomachal 

 surface shall become the epidermis, and yet continue 

 to live and enjoy itself, and the animal suffers very 

 little by these apparently cruel operations, 



'Scarce seems to feel, or know 

 His wound,' 



for, before the lapse of many minutes, the upper half 

 of a cross section will expand its tentacula and catch 

 prey as usual \ and the two portions of a longitudinal 

 division will, after an hour or two, take food and 

 retain it. A polype cut transversely in three parts 

 requires four or five days in summer, and longer in 

 cold weather, for the middle piece to produce a head 

 and tail, and the tail part to get a body and head, 

 which they both do in pretty much the same time." 



You will often notice some very interesting para- 

 sites upon the various species of Hydra. One very 

 curious little fellow delights to run up and down .the 

 hydra's tentacles, like a miniature railway-truck. In 

 form the creature resembles a dice-box, only it is as 



