104 The Unity of the Organism 



series whatsoever, is a determinate thing; it is what it is 

 partly because of its position in the series regardless of 

 whether the physical or other producing agent of the dif- 

 ferent series be the same or wholly different. 



Even this purely structural formal basis establishes 

 the fact of a measure of integratedness for all individual 

 organisms in which the phenomenon appears. But to leave 

 the subject at that would be superficial and unsatisfactory 

 indeed. However, reflection makes it almost certain that 

 there is some sort of causal basis for the phenomena. This 

 conclusion follows first from the fact that the series result 

 from the growth of the organism, and second from the cer- 

 tainty, at least in many cases, that the continuance of life 

 of the individual involves the maintenance of the series, this 

 in turn involving some measure of metabolic interdepen- 

 dence among the members of the series. 



Attempted Causal Explanation of These Series 



For establishing the general truth of this type of inte- 

 gration we need not, in strictness, go any further than we 

 have gone. Nevertheless, the importance of the subject 

 justifies a few remarks on attempts that have been made to 

 explain the series causally. The best known of these comes 

 from botanists, and conceives that the diminishing series of 

 leaves and other structures, seen with more or less distinct- 

 ness almost universally among plants, is due to the increas- 

 ing remoteness of the successive parts from the roots of the 

 plant, that is, from the main source of the plant's food. It 

 is obvious, however, that this explanation is not of general 

 application, since in animals the food does not come from a 

 root system which anchors the organism to its food-yielding 

 medium. Nor is it possible to bring the series in all animals 

 into correlation with a blood circulatory system, as their 

 existence in many coelenterates, hydroids and alcyonarians 



