20 MARINE BIOLOGICAL LABORATORY. 



which merges their individualities into an individuality 

 of a higher order. The tendency towards unity, as 

 specialization advances is nowhere more strikingly illus- 

 trated than in the progress from the lower to the higher 

 segmented animals. In the lower annulose types, the 

 individual represents a chain of segments or somites, 

 which we may regard as so many individuals which 

 have arisen as buds, one after the other, from before 

 backwards, but have remained connected in the order 

 of origin. These somites retain their individuality to 

 such an extent that they are not killed by artificial 

 separation, and indeed often undergo spontaneous 

 fission. 



As we glance along the line of forms terminating in 

 the Myriopods, the Crustaceans, the Insects, and the 

 Arachnids, we find the individualities of the somites 

 more and more subordinated to that of the chain they 

 compose. There is a progressive consolidation, which, 

 in its extreme phases, more or less completely obliterates 

 the traces of articulation. The illustration might be 

 extended to the vertebrates, but that would be needless. 

 Let me add only, as one of the broadest conclusions to 

 be drawn from such facts as we have been considering, 

 that tJie grade of specialization attained in any group of 

 07ganisnis determines its rank in the scale of life and in- 

 telligence. 



In each order of units, specialization seems to have 

 its limit in the highest possible integration of its com- 

 ponent elements. When this limit is reached, progress 

 is arrested. The only way then open for advance lies 

 in combining these units into units of a higher order. 

 In this combination is given the possibility of a 



