THE DETERMINATION OF DOMINANCE. 323 



rather closely allied to L. muUitceniata, which is also suggestive 

 of having arisen, or of being in the process of arising, through 

 hybridization. 



These conditions in nature are of course difficult or impossible 

 to check and verify, because the past is absolutely unknown, 

 and little or no indication of what it has been can be obtained 

 from any source. The materials in museums and the records 

 by systematists are utterly useless for this purpose. Appar- 

 ently, the only way of attacking this problem is the one which 

 I have adopted of placing colonies in isolated locations, or in 

 cages, there to carry out the process of interbreeding and form- 

 ing of hybrid combinations as would occur in nature. 



Discussion. 



Neo-Mendelism, The Factorial Hypothesis, and Theories of 

 Germ- Plasm Composition. 



The essence of Neo-Mendelism is based upon the actual experi- 

 mental evidence of many workers, and is the idea that such of 

 the attributes of organisms as show this type of behavior are the 

 product of two factors which come into the fertilized egg, one 

 from each parent, and that in gametogenesis these factors are 

 distributed among the gametes by some process which is symbol- 

 ized as "segregation." This factorial point of view is in no wise, 

 of necessity, to be tied to or confounded with such speculations 

 as the id-determinant-biophore fabric of Weismann, nor with 

 the pangene complex of DeVries, which have no foundation in 

 fact. 



I doubt very much if Davenport (1910) will find many Neo- 

 Mendelians willing to subscribe to his statement — "In studying 

 heredity our attention must often be focused on the ontogenesis 

 of the different characters, and we are sometimes inclined to 

 regard the adult character as the product of the course of onto- 

 genesis. But this is a superficial way of looking at things; the 

 determiners of all characters are in the germ-plasm and together 

 they direct the development of one part after another in orderly 

 succession; a modernized form of the preformation doctrine 

 seems logically necessary." That the determiners of all charac- 



