THE MORPHOLOGICAL COMPOSITION OF ANIMALS. 91 



into Amcsba-likc portions, capable of moving about inde- 

 pendently. If we bear in mind how analogous are the 

 extreme extensibility and contractility of a Hydra's body 

 and tentacles, to the properties displayed by the sarcode 

 among IMiizopods; we may infer that probably the move- 

 ments and other actions of a Hydra, are due to the half- 

 independent co-operation of the Amoeba-\ike individuals 

 composing it. 



§ 202. A truth which we before saw among plants, we 

 here see repeated among animals — the truth that as soon as 

 the integration of aggregates of the first order into aggregates 

 of the second order, produces compound wholes so specific in 

 their shapes and sizes, and so mutually dependent in their 

 parts, as to have distinct individualities ; there simultaneously 

 arises the tendency in them to produce, by gemmation, other 

 such aggregates of the second order. The approach towards 

 definite limitation in an organism, is, by implication, an ap- 

 proach towards a state in which growth passing a certain 

 point, results, not in the increase of the old individual, but 

 in the formation of a new individual. Thus it happens that 

 the common polype buds out other polypes, some of which 

 very shortly do the like, as shown in Fig. 148: a process 

 paralleled by the fronds of 

 sundry Algce, and by those 

 of the lower Jungermanni- 

 acece. And just as, among 

 these last plants, the pro- 

 liferously-produced fronds, 

 after growing to certain 

 sizes and developing root- 

 lets, detach themselves from their parent fronds; so among 

 these animals, separation of the young ones from the bodies 

 of their parents ensues when they have acquired tolerably 

 complete organizations. 



There is reason to think that the parallel holds still fur- 



