218 MENDELISM 



With three such factors we should expect only one 

 of each parent type to appear among sixty-four 

 individuals. 



There seems to be no reason for doubting that the 

 total number of visible factors, even, which go to 

 make up the total shape of a flower may be consider- 

 ably greater than this ; and the number of invisible 

 allelomorphs upon which these depend may be pro- 

 portionately more numerous still. In such a case, in 

 an experiment where the total number of offspring 

 grown was limited, types like the original parents 

 might never be seen, simply because the sample taken 

 was not sufficiently large. 



Again, we have to consider the possibility of a 

 differential fertility among the various allelomorphic 

 combinations. This might lead to an intermediate 

 form, actually breeding true in spite of the fact that 

 segregation was going on in its germ -cells. The 

 possibility has to be borne in mind that among the 

 offspring of two widely different species those indi- 

 viduals which more nearly resemble their immediate 

 hybrid parent may have a better chance of survival 

 than the forms which have more characters in common 

 with a single pure grandparent. The only piece of evi- 

 dence we have bearing upon this point is the fact that we 

 know the hybrid form itself to be capable of surviving. 



De Vries has published a very interesting observa- 

 tion, which ought to be mentioned in this connec- 

 tion. It appears that two forms of (Enothera, which 

 originated in a cross, and are distinguished as 

 Lata and Velutina respectively, possess female gametes 



