INTRODUCTION xxL 



requires the possibility of a distinct symbiotic effort or 

 " elan " by the parts entering into the alliance, i.e., the evolu- 

 tion of sufficient rejuvenating and elevating power during the 

 process of fertilisation, without which the latter is of not much 

 avail and sterility ensues. 



What is it that confers these powers, this "elan" in 

 particular, upon organisms? I hold that it is their biological 

 conduct which is primarily responsible for genuine genetic- 

 strength, for it is this conduct which, if symbiogenetic, 

 purchases additional outside (biological) support in virtue of 

 the valuable correspondences (biological correlations) which it 

 sets up. I hold that heritable biological correspondences con- 

 stitute in great part the wealth of a species, and that therefore 

 the mechanism of the inheritance of acquisitions must be looked 

 for among these correspondences and their results quite as much 

 as in the individual characters and powers of the organism 

 itself, that is to say, that some of the factors making up such 

 inheritance are in the (symbiotic) environment and cannot 

 operate unless the symbiotic co-operation is fully carried out. 



My interpretation of genetic phenomena, in particular 

 those bearing on Mendelian inheritance, may or may not com- 

 mend itself to present workers in the field of genetics, but I 

 venture to predict that it will appeal increasingly to those who 

 are in search of causal factors and of qualitative analysis- 

 generally. 



The same remark applies to the treatment I have given in 

 subsequent chapters to Bionomics, Pathogenesis, Orthogenesis, 

 and Psychogenesis respectively. In these chapters I wished,, 

 among other things, to show the need of Bio-Economics as 

 applying to the whole field of Biology. 



That the Nitrogen problem had to bulk large in these con- 

 siderations is only in keeping with the general importance of 

 this problem, so acutely and so widely felt in Biology, in 

 Bio-Chemistry, as in Medicine, Genetics, and in Agriculture. 

 My conclusion is that Nitrogen is a good servant but a bad 



