Modification of Germinal Constitution oj Organisms 247 



to preserve the extreme and by rigorous selection to eliminate 

 the mean, and the other which tends to eliminate the 

 extreme and preserve the mean. Rigorous artificial selec- 

 tion makes the preservation of the extreme the more potent 

 of the two, and results in rapid divergence, but not in 

 unlimited divergence, and when this selective process ceases 

 the natural selective process again becomes operative with 

 the result that there is rapid regression to the mean racial 

 standard. 



Confusion exists in many records of selection experi- 

 ments, due to the presence of biotypes or phenotypes, so 

 that the selection is really a process of separating the present 

 elemental forms. In the above-cited experiments only one 

 biot\'pe was present and this was not capable of being 

 changed by selection — cjuantitative — beyond the normal 

 range. The bearing and necessity of working with one 

 biotxpe in this selection work and not with a complex of 

 several is well known to all students of genetics at the present 

 da^^ although not adecjuately appreciated by practical 

 breeders. 



The facts concerning inconstancy and reversion are well 

 known to breeders of animals and plants, who must practice 

 constant selection to maintain the standard of their artifi- 

 cialh' improved races. Is it possible to produce, by a selecti^'e 

 process, modifications which are permanent and which do 

 not revert on the cessation of the selective action, which 

 maintain themselves when brought in contact with the 

 parent species, and which maintain themsehes when placed 

 in nature ? In selective processes of this kind, amount 

 is a negligible cjuantity; only pattern arrangement need be 

 considered. In other words, those difl'erences in the consti- 

 tution of the organism which localize specific characters 



