60 LEISURE-TIME STUDIES. 



has led us far afield into the domain of metaphysics, and 

 has in some measure alienated us from our more sober study of 

 the commonplace hydra. We have, however, noted that our 

 polype forms a text for the illustration of some points highly 

 interesting to humanity at large ; and in what remains to be 

 told of its life-history we shall find exemplified several other 

 features of highly interesting, if not of most remarkable kind. 



Of these latter features, probably the most notable relate 

 to the various modes in which the hydra may reproduce its 

 kind. We have already noted how the animal makes pro- 

 vision for the wants of its own existence, and how it repairs 

 the local and continually occurring death of its parts by the 

 reception and digestion of food, and by the circulation of 

 the products of nutrition from cell to cell of its body. Such 

 a view of the polype's organisation, however, presents us, 

 after all, with only a one-sided aspect ; and, like most partial 

 and incomplete surveys of things, our ideas of the polype's 

 life-history are apt to become erroneous and liable to mis- 

 construction. Every living being, in addition to the duty 

 imposed upon it of repairing its individual loss of substance, 

 has to bear a share in the reparation of the losses which 

 death is the means of inflicting on its species or race. 

 Through the processes of reproduction and development, 

 new beings are ushered into the field of active life, to take 

 part in carrying on the life of the species, just as the process 

 of nutrition made good the wants and supplied the exigencies 

 of the single form. 



The Harveian motto, Omne ex ovo, holds good in the case 

 of the hydra, inasmuch as we find that animal, in summer 

 more particularly, may be seen by aid of special organs 

 (Fig. 2, g, h) to produce eggs, from which, through a process 

 of regular and defined development, new hydrse are produced. 

 But we may concern ourselves less with this normal phase 

 of development, than with certain strange and out-of-the- 

 way features which our polype may be observed to exhibit. 

 There are very few persons, outside the ranks of biologists, 

 who would be inclined to associate a veritable process of 



