80 thf: vital functions. 



derful power of repairing all sorts of injuries, 

 and of restoring parts which have been removed. 

 These animals are found to bear with impunity 

 all sorts of mutilations. If the tentacula be cut 

 off, they grow again in a very short time : the 

 whole of the fore part of the body is, in like 

 manner, reproduced, if the animal be cut asun- 

 der ; and from the head which has been removed 

 there soon sprouts forth a new tail. If the head 

 of the hydra be divided by a longitudinal section, 

 extending only half way down the body, the cut 

 portions will unite at their edges, so as to form 

 two heads, each having its separate mouth, and 

 set of tentacula. If it be split into six or seven 

 parts, it will become a monster with six or seven 

 heads ; if each of these be again divided, ano- 

 ther will be formed with double that number. 

 If any of the parts of this compound polypus be 

 cut off, as many new ones will spring up to re- 

 place them ; the mutilated heads at the same 

 time acquiring fresh bodies, and becoming as 

 many entire polypi. Fig. 245 represents a hydra 

 with seven heads, the result of several operations 

 of this kind. The hydra will sometimes of its 

 own accord split into two ; each division be- 

 coming independent of the other, and growing 

 to the same size as the original hydra. Trembley 

 found that different portions of one polype might 

 be engrafted on another, by cutting their sur- 

 faces, and pressing them together ; for by this 



