284 Evolution and Adaptation 



with the pollen plant. From this we may conclude that, if two 

 varieties differing in a large number of characters are crossed, 

 the hybrid might get some of its dominant characters from 

 one parent, and other dominant characters from the other 

 parent, so that, unless the individual characters themselves 

 were studied, it might appear that the hybrids are interme- 

 diate between the two parents, while in reality they are only 

 combinations of the dominant characters of the two forms. 

 But even this is not the whole question. 



Mendel points out that, from knowing the characters of 

 the two parent forms (or varieties), one could not prophesy 

 what the hybrid would be like without making the actual 

 trial. Which of the characters of the two parent forms 

 will be the dominant ones, and which recessive, can only be 

 determined by experiment. Moreover, the hybrid characters 

 are something peculiar to the hybrid itself, and to itself alone, 

 and not simply the combination of the characters of the two 

 forms. Thus in one case a hybrid from a tall and a short 

 variety of pea was even taller than the taller parent variety. 

 Bateson lays much emphasis on this point, believing it to be 

 an important consideration in all questions relating to hybri- 

 dization and inheritance. 



The theoretical interpretation that Mendel has put upon 

 his results is so extremely simple that there can be little 

 doubt that he has hit on the real explanation. The results 

 can be accounted for if we suppose that the hybrid pro- 

 duces egg^cells and pollen-cells, each of which is the bearer 

 of only one of the alternative characters, dominant or reces- 

 sive as the case may be. If this is the case, and if on an 

 average there are the same number of egg-cells and pollen- 

 cells, having one or the other.. of these kinds of characters, 

 then on a random assortment meeting of egg-cells and 

 pollen-cells, Mendel's law would follow. For, 25 per cent of 

 dominant pollen grains would meet with 25 per cent dominant 

 egg-cells ; 25 per cent recessive pollen grains would meet with 



