282 CHAPTERS ON EVOLUTION. 



tree may thus be viewed, in that three generations of polypes remain 

 connected as they were produced by the parent stem. The hydra 

 thus converts itself normally into a compound colony through this 

 process of budding. But this state of matters is, at the most, transi- 

 tory and temporary in hydra-existence. The budded individuals,, 

 sooner or later, break contact with the parent-body, and pass to seek 

 a new lodgment and to begin life on their own account ; leaving the 

 parent, single as before, but connected, as we shall presently note,, 

 to the free offspring by ties which our transcendental philosophy 

 makes clear and plain. It may lastly be remarked that, in respect of 

 structural constitution, the closest similarity exists between a cup- 

 sponge and a hydra. Both possess tubular bodies, and both con- 

 sist of two cellular layers. Modern zoology has emphasised this 

 likeness by placing the sponges in the same great group ( Calenterata) 

 which contains the hydra and zoophytes. It is conceivable enough, 

 indeed, that a hydra is simply a specialised sponge-form possessing 

 its compound and colonial nature somewhat disguised beneath an 

 apparently single personality. 



The constitution of a " zoophyte" (Fig. 189) is mere matter of 

 repetition after the recital of the hydra's peculiarities. The plant- 

 like Sertularian or "sea-fir" (Fig. 189, a), which we dredge by the 

 hundred, growing on oyster- shells ; or the Flustra (Fig. 190) or 

 " sea-mat " of higher organisation than the " sea-firs," but pre- 

 senting likewise the aspect of a marine plant present us each 

 with a veritable colony of more or less similar beings, united 

 in the bonds of close relationship. Thus the sea-fir, as the type 

 of the true zoophyte, bears on its branches hundreds of little 

 cups (Fig. 189, b, d), each of which contains an animal strictly corre- 

 sponding in structure to a hydra (Fig. 188). This multitude of animal 

 bodies is bound together in intimate union. The stem and branches 

 are hollow, and each little mouth and body, digesting the food its 

 tentacles have captured, transmits that food to swell the general 

 stream of nutriment circulating through the tree-like fabric. Thus 

 we find the principle of co-operation herein illustrated in plainest 

 guise. Each little animal derives its own share of nutriment from 

 the general store it has helped to manufacture ; and the exercise of 

 the principle in question is all the more perfect, in that its practice is 

 free from those petty jealousies and personal inducements to infringe 

 the duty of equal and harmonious work which usually beset the 

 co-operative societies of higher existence. The remaining points 

 which call for notice in the history of the zoophyte may be shortly 

 summed up. The little members of the colony are continually dying 

 off as the result of their life-work, but their place is supplied and the 

 colonial loss repaired by the production of new buds. As leaves 

 fall from a tree and are replaced by the growth of new buds, so the 



