depends largely on the supply of fo^d and on temperature. If a 

 rapidly budding Hydra be transferred to water in which there is 

 little or no food to be obtained, the formation of buds will be 

 stopped, and those already formed may even be absorbed, A single 

 Hydra may develop more than one bud at once, and these may 

 develop secondary buds before separating from the parent a,nimal. 

 In this way temporary colonies may be formed, which however^ 

 sooner or later, break up into their component units. 



Hydra can also multiply by fission, i.e., it can be cut in two, 

 and each half will become a perfect animal. The process of fission, 

 however, very rarely occurs naturally. 



On this subject Johnston on " British Zoophytes " writes :— " If 

 the body is halved m any direction each half in a short time grows 

 a perfect hydra ; if it is cut into four or eight or even minced up' 

 into forty pieces each continues alive and develops a new animal, 

 which is itself capable of being multiplied in the same extra- 

 ordinary manner. If the section is made lengthwise, so as to 

 divide the body into two or more slips, merely connected by the 

 tail, they are speedily resoldered like some heroes of fairy tale, into 

 one perfect whole ; or if the pieces are kept asunder each will be- 

 come a polyp : and thus we may have two or several polypes with 

 only one tail between them, but if the section be made in a contrary 

 direction from tail towards the tentacles, you produce a monster 

 with two or more bodies and only one head. If the tentacles — the 

 organs by which they take their prey, on which their existence 

 might seem to depend — are cut away, they are reproduced, and the 

 lopt off parts do not remain long without a new body. 



" If only two or three tentacles are embraced in the section, the 

 result is the same, and a single tentacle 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 the unscarred parts ; when a polype is in- 

 troduced by the tail into another's body the two unite and form 

 one individual ; and when a head is lopt off it may be safely 

 engrafted on the body of any other which may chance to want 

 one .... And the creature even suffers very little by these 

 apparently cruel operations. 



" Scarce seems to feel, or know 

 " His wound, 

 *♦ for before the lapse of two minutes, the upper half of a cross 

 section will expand its tentacles and catch prey as usual ; and the 

 two portions of a longitudinal division will after an hour or two 

 take food and retain it." 



I have omitted one sentence from the extract, as I have already 

 alluded to it as discussed and disproved by modern scientists. 



