522 POPULAR SCIENCE MONTHLY. 



darts. Then begins a tussle which generally ends in the captive 

 being conveyed to the mouth. Occasionally some strong swim- 

 mer may get away, but, unless he is armor-plated, he has but 

 little chance of his life, for a poisoned dart is most probably 

 imbedded in his body. Sometimes a victim is very troublesome, 

 and, in order to get it safely into its mouth, the tentacle itself 

 must also be partially ingulfed, and it remains so until the mor- 

 sel is quiet, and even until digestion has begun. As the food is 

 drawn in, you can see the body swell, and in some cases become 

 quite pear-shaped. After a while the swelling subsides, and, 

 after all the useful part of the food has been extracted, the rest is 

 ejected at the same place at which it entered. It is most inter- 

 esting to watch the instinctive motions of this creature, which is 

 totally destitute of what we should call brain. 



Hitherto we have spoken only of a single individual, but we 

 must now notice a startling fact. The hydra is multiplied 

 according to the usual law by eggs, it is true ; but also in 

 another way. You can not examine a group in summer time 

 without finding that they "bud." You see the trunk of one 

 bearing a second, perfect in every respect, except that it is con- 

 nected with its parent, instead of resting on a foreign substance. 

 It has sprouted out from the parent stock, like a sucker from a 

 tree. It may break off. after a while and seek an independent 

 resting place, or it may send out a bud from its own stem, which 

 in its turn may do the same, and all may remain attached for 

 some time. While this connection lasts, each member of the 

 compound body forages at his own " will," but the tubes of each 

 connect with the trunk of the next, and so with the parent 

 stomach. Thus they form a colony in which each member helps 

 to maintain every other member by his labor. A sight of such a 

 colony of hydras, the working of which is visible to the naked 

 eye, helps one to understand many other similar forms of animal 

 life as, for instance, the corals, which form colonies by budding. 

 As many as four generations of hydras have been seen on one 

 stem, so that there is some reason for likening such a community 

 to " a living genealogical tree." 



By a number of experiments with which some of us will 

 scarcely sympathize, Trembley and those who have repeated his 

 investigations have brought out many astounding facts about 

 these animals. If you cut one in two across the trunk, the upper 

 part floats off and resumes its voracious habit in a new locality ; 

 while the lower portion remains, develops a new set of tentacles, 

 and goes on just the same as if nothing had happened. Nay, you 

 may cut a hydra into five or six pieces, and each will make a sepa- 

 rate animal. If one is divided into two vertically, the two halves 

 close up, and again you have two individuals. Trembley sue- 



