OUR NATURAL INHERITANCE 65 



a sperm-cell of somewliat different genetic history may 

 account for the emergence of new patterns. 



Experiments show that a single-celled organism — 

 a Protozoon or Protophyte — may be changed by 

 changes in the medium in which it lives. Similarly it 

 may be that the egg-cells or sperm-cells within the 

 body of the parents are influenced by changes in the 

 complex medium (the blood or the lymph) by which 

 they are kept alive. 



There is also some very suggestive evidence that 

 environmental influences of a searching sort, such as 

 changes of climate and food, may saturate through the 

 organism and act as variational stimuli on the germ- 

 cells, pulling the trigger of their changefulness. It 

 may be in this way that some poisons are able to exert 

 a more or less direct deteriorative influence on the germ- 

 cells and thus on the next generation. 



It may also be that since a germ-cell is a living cell 

 with a very complicated endowment of hereditary 

 factors, it spontaneously experiments with these, 

 arranging them in different ways, just as a slipper- 

 animalcule may break down and reorganise its nuclear 

 structure, just as an arenaceous Foraminifer may 

 apparently pick and choose external materials — micro- 

 scopic pebbles, sponge spicules, mica platelets, and so 

 on in building up its external shell. But, as we have 

 confessed, biologists are only nibbling at the problem 

 of the origin of the distinctively new. Applying this 

 to mankind, we see that it is impossible to suggest any 

 recipe for the production of genius. At the same time, 



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