INADEQUACY OF NATURAL SELECTION, ETC. 623 



degrees, directly or indirectly, to the multiplication of the stirp ; 

 whence failure to account for various changes ascribed to it. 

 And we have seen that it yields no explanation of the co-adapta- 

 tion of co-operative parts, even when the co-operation is rela- 

 tively simple, and still less when it is complex. On the other 

 hand, we see that if, along with the transmission of generic and 

 specific structures, there tend to be transmitted modifications 

 arising in a certain way, there is a strong a priori probability that 

 there tend to be transmitted modifications arising in all ways. 

 We have a number of facts confirming this inference, and show- 

 ing that acquired characters are inherited as large a number as 

 can be expected, considering the difficulty of observing them and 

 the absence of search. And then to these facts may be added 

 the facts with which this essay set out, concerning the distribu- 

 tion of tactual discriminativeness. AA'hile we saw that these are 

 inexplicable by survival of the fittest, we saw that they are 

 clearly explicable as resulting from the inheritance of acquired 

 characters. And here let it be added that this conclusion is con- 

 spicuously warranted by one of the methods of inductive logic, 

 known as the method of concomitant variations. For throughout 

 the whole series of gradations in perceptive power, we saw that 

 the amount of the effect is proportionate to the amount of the 

 alleged cause. 



II. 



Apart from those more special theories of Professor Weismann 

 I lately dealt with, the wide acceptance of which by the biological 

 world greatly surprises me, there are certain more general theo- 

 ries of his fundamental theories the acceptance of which 

 surprises me still more. Of the two on which rests the vast 

 superstructure of his speculations, the first concerns the distinc- 

 tion between the reproductive elements of each organism and 

 the non-reproductive elements, lie says : 



" Let us now consider how it happened that the raulticellular animals and 

 plants, which arose from unicellular forms of life, came to lose this power of 

 living for ever. 



"The answer to this question is closely bound up with the principle of 

 division of labour which appeared among multicellular organisms at a very 

 early stage. 



" The first multicellular organism was probably a cluster of similar cells, 

 but these units soon lost their oriirinal homogeneity. As the result of mere 

 relative position, some of the cells were especially fitted to provide for the 

 nutrition of the colony, while others undertook the work of reproduction." 

 (Essays upon Heredity, i, p. 27) 



Here, then, we have the great principle of the division of 

 labour, which is the principle of all organization, taken as prima- 



