SEGREGATION OF THE GAMETES 169 



same percentage of dominants and recessives as the preceding 

 generation. From this it may be concluded that from the 

 hybrids when self-fertilised are obtained 25 per cent, pure 

 dominants ; 50 per cent, impure dominants that is, plants 

 exhibiting the dominant character but containing the 

 recessives; and 25 per cent, pure recessives. In succeed- 

 ing generations, the same proportions of pure dominants, 

 impure dominants, and pure recessives are always obtained 

 from the impure dominants. 



Mendel assumed that these characters, with which he 

 experimented, were represented by units or entities in the 

 gametes. In each of the pure-bred parents from which 

 the first generation of hybrids was produced, there would 

 be only one kind of entity. In the first generation of 

 hybrids, however, both entities representing the characters 

 must be present. He supposed that in the production of 

 the gametes of the hybrids, these entities representing two 

 opposing characters separated from each other, so that half 

 the gametes contained entities representing one character, 

 and half contained entities representing the other. In the 

 production of the next generation, according to the laws of 

 chance, as the number of each kind of gamete would be 

 equal, 50 per cent, would fuse with other gametes like them- 

 selves, 50 per cent, with the opposite kind of gamete. Of 

 the gametes that fused with others like themselves, half 

 would be dominants, and half would be recessives. The 

 results in the second generation then would be 25 per cent, 

 of individuals produced from two gametes both containing 

 the dominant character, 25 per cent, produced by the fusion 

 of two gametes both containing the recessive character, 

 and 50 per cent, by the fusion of two gametes, one con- 

 taining the dominant, the other the recessive character. 

 A very simple illustration of this phenomenon may be 

 shown experimentally by putting 100 white beans and 

 100 black beans into a bag. These are supposed to 

 represent the two different kinds of gametes whose fusion 

 is to produce the second generation of hybrids. Now, if 



