.90 MORPHOLOGICAL DEVELOPMENT. 



weapons in like ways with like efficiency ; aud could, if 

 tailed on, similarly perform various manual processes directly 

 or indirectly conducive to their welfare. But when on the 

 word of command "right face," they so place themselves 

 that each has one of his neighbours before him and another 

 behind him, nearly all of them become incapacitated for 

 fighting and for many other actions. They can walk or run 

 one after another, so as to produce movement of the file in 

 the direction of its length ; but if the file has to oppose an 

 enemy or remove an obstacle lying ia the line of its march, 

 the front man is the only one able to use his weapons or 

 hands to much purpose. And manifestly such an arrange- 

 ment could become advantageous only if the front man pos- 

 sessed powers peculiarly adapted to his position, while those 

 behind hiua facilitated his actions by carrying supplies, &c. 

 This simile, grotesque as it seems, serves to convey better 

 perhaps than any other could do, a clear idea of the relations 

 that must arise in a chain of individuals arising by gemma- 

 tion, and continuing permanently united end to end. Such 

 a chain can arise by natural selection, only on condition that 

 combination is more advantageous than separation ; and for 

 it to be more advantageous, the anterior members of the series 

 must become adapted to functions facilitated by their posi- 

 tions, while the posterior members become adapted to func- 

 tions which their positions permit. Hence, survival of the 

 fittest must tend continually to establish types in which the 

 connected individuals are more unlike one another, at the 

 same time that their several individualities are more dis- 

 guised by the integration consequent on their mutual 

 dependence. 



Such being the anticipations warranted by the general 

 lawS' of evolution, we have now to inquire whether the-o 

 are any animals which fulfil them. Very little search 

 suffices ; for structures of the kind to be expected are abund- 

 ant. In that great division of the animal kingdom called 

 Annulosa, especially if the Annuloida be regarded as part of 



