164 SYMBIOGENESIS 



heredity remains, fundamentally, as far from solution as it 

 was in Darwin's day. 



It has been found in some cases that, " In order to obtain 

 Mendelian segregation, variations occurring in a race occupy- 

 ing the same geographical area must be crossed ; but that when 

 characters in geographically separate races are crossed, they 

 blend," which again would seem to point to the fact that 

 Mendelian phenomena are but part and parcel of the great 

 qualitative genetic processes "the long protracted gestation" 

 of nature. The analogy with the superiority of cross- 

 fertilisation and cross-feeding over in-breeding and in- 

 feeding must indeed here suggest itself. If fertilisation is 

 subservient, as I hold, to productiveness and to organic 

 integrity in general, we can see how for bio-economic (sym bio- 

 genetic) reasons greater effectiveness and greater stability are 

 in the end obtained by the union of slightly but sufficiently 

 differentiated units from different areas than by the union of 

 very homogeneous ones from the same area. That Nature 

 abhors perpetual in-feeding and perpetual in-breeding, that 

 there exists a biological antagonism to stagnancy, is thus 

 another way of stating the "instability of the homogeneous! " 



Dr. Walker lays great stress on the fact that no two cells 

 are ever exactly alike, and that variations have been present 

 from the very first stage, " otherwise evolution would abso- 

 lutely have been impossible. . . . Offspring must always 

 vary from their parents, and offspring of the same parents from 

 each other." 



" For the origin of this property of varying we must there- 

 fore go back to the origin of life itself, and it seems a work of 

 supererogation to invent theories as to the causes of variations 

 during the later stages of evolution and to treat them as if they 

 had not been there all along." 



The tendency to vary, then, is as old as the hills; and so, 

 let us remember, is the economic problem, and so also the need 

 of specialisation, of reciprocal differentiation, i.e., of sym bio- 

 genesis if organisation is to be produced, to survive and to 



