96o LIFE : OUTLINES OF GENERAL BIOLOGY 



and nutrition on one hand, with those subserving reproduction 

 on the other, of which we have already urged the evolutionary 

 significance and the interpretative value over so many fields, 

 hitherto considered too separately. And it is also reciprocally evident 

 that our presentation remains too much as it was in our earlier 

 volumes, and so needs fuller development, with the help of the 

 methods and results of both Thompson and Child. 



It is also of the essence of all these three doctrines, that without 

 interfering with the remarkable progress of genetic research, they 

 return to the investigation of that variability of the organism itself, 

 which has been so often left out of account since Weismann's 

 concentration and insistence upon the essential reproductive ele- 

 ments and processes: valuable and stimulating though that has been. 



Again, is it not evident from all these three variously developed 

 viewpoints ahke, that with their closely kindred and fairly compre- 

 hensive interpretations of changes in growth and form together, 

 the long customary and detailed view of variation, so essentially 

 mechanistic — indeed, so closely machine-like — has, largely at least, 

 to be dispensed with? For on all three later lines of interpretation, 

 "small variations" appear as the consequences, in details, of the 

 general growth of the organism as a living unity. The difficulty, on 

 mechanistic principles, of explaining the marvellous co-adaptation 

 of variations, if arising separately and distinctly, and of this also 

 by natural selection alone — a difficulty which Darwin indeed so 

 candidly admitted — thus wellnigh disappears; and in favour of 

 more continuous and comprehensive views of their origin, in course 

 of the growth and development of the whole being. 



Variations need for their survival a complex adaptation, at once 

 in their own particular functioning and structure, and also to the 

 organism as a whole; with its complemental adaptation to them in 

 its turn, and with change accordingly. From the Darwinian point of 

 view, these variations, in absence of any definite theory, remain 

 "spontaneous and indefinite"; for though cases of "correlation of 

 variations" have of course been considered by Darwin and later 

 writers, these remain but empirically recorded, and without ex- 

 planation. The neo-Darwinian view, with its insistence on varia- 

 tions as fundamentally germinal rather than somatic, has concen- 

 trated its inquiries upon the sex-elements and ovum, and there into 

 a sort of dice-throwing among the multifarious possibilities of the 

 chromosomes. This view of variation thus remains, indeed more 

 than ever, on purely mechanistic and morphological lines; and it 

 still lacks complemental physiological explanation, which should 

 accompany it and carry it onwards into a rationale of development. 

 Conversely, all the above three contributions to the understanding 

 of this process have still to be coadjusted with the results of the 

 geneticists. 



