THE MORPHOLOGICAL COMrOSITION OF ANIMALS. 87 



kind is drawn on a small scale in Fig. 159, and a portion of 

 tlie same on a larger scale in Fig. 158, tliere is a combination 

 of the individuals into annular clusters, wliicli are themselves 

 imbedded in a common gelatinous matrix. And in this 

 group there are integrations even a stage higher, in which 

 several such clusters of clusters grow from a single base. 

 Here the compomiding and re-compounding, appears to 

 be carried further than anywhere else in the animal 

 kingdom. 



Thus far, however, among these aggregates of the third 

 order, we see what we before saw among the simpler aggre- 

 gates of the second order — we see that the component indi- 

 vidualities are but to a very small extent subordinated to the 

 individuality made up of them. In nearly all the forms in- 

 dicated, the mutual dependence of the united animals is so 

 slight, that they are more fitly comparable to societies, of 

 which the members co-operate in securing certain common 

 benefits. There is scarcely any specialization of fimctions 

 among them. Only in the last type described do we see a 

 number of individuals so completely combined as to simulate 

 a single indi\ddual. And even here, though there appears to 

 be an intimate community of nutrition, there is no physio- 

 logical integratioii beyond that implied in several mouths and 

 stomachs ha\dng a common vent. 



^ 204. TFe come now to an extremely interesting ques- 

 tion. Does there exist in other sub-kingdoms composition of 

 the third degree, analogous to that which we have found so 

 prevalent among the Ccekntemta and the MoUuscoida ? The 

 question is not whether elsewhere there are tertiary aggregates 

 produced by the branching or clustering of secondary aggre- 

 gates, in ways like those above traced ; but whether elsewhere 

 there are aggregates which, though otherwise unlike in the 

 arrangement of their parts, nevertheless consist of parts so 

 similar to one another that we may suspect them to be 

 united secondary aggregates. The various compound typefi 



