134 SYMBIOGENES1S 



characters was somehow not relished by nature, and therefore 

 failed to yield a satisfactory and permanent blend, i.e., that 

 we have in such an instance behaviour not far removed from 

 that usually termed mutual infertility. If this be so, segrega- 

 tion may be regarded as a kind of protection of desirable 

 (blended) inheritance, which may again proceed unobstructed 

 as soon as undesirable foreign strains are eliminated in toto. 

 I should say that the partial mutual infertility disclosed by 

 Mendelian segregation must be viewed as one of the means of 

 safeguarding the great ultimate (bio-economic) interests of the 

 biological world, and that the incompatibilities here concerned 

 are chiefly constituted by bio-economic and related bio- 

 chemical factors. Will the union be a success from the bio- 

 economic point of view, that is the question in every union of 

 " gametes." Whilst in nature this is determined by various 

 qualitative tests, such as prepotency and resistance to disease, 

 the breeder, wittingly or unwittingly, generally sets aside the 

 natural factors (together with other vital correspondences), 

 and for a time is able to "breed" for the particular purposes 

 he has in mind or, as the case may be, quite indiscriminately, 

 although these may not be by any means the purposes of 

 symbiogenesis. He relies for results on natural "endow- 

 ments," but ignores their origin, their true significance and 

 value. 



If then, according to Mr. Shelton, it be that Mendelian 

 inheritance accomplishes in various ways the same purpose as 

 the mutual infertility of allied species, we may also say that 

 it represents the natural tendency to prevent the very thing 

 that domestication so generally induces, namely, loss of 

 genuine bio-economic diversification and resultant retrograde 

 compatibilities (fertility of a sort!), and we shall, therefore, 

 be on our guard against all inferences from artificial experi- 

 ments which fail to make allowance for the qualitative (bio- 

 economic) purposes of nature, and deal with the most varying 

 orders of factors in a promiscuous manner. 



In Nutrition and Evolution (1909), I have already 



