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THE AMEBIC AN NATURALIST [Vol. XL VIII 



Close selection, of course, tends toward the same end (homozygosis), 

 but not with the rapidity or certainty of self-fertilization. 



This idea is further shown by their statements under the head- 

 ing "Extension of Conclusions to the Animal Kingdom" (pp. 

 39-43). 



A little later Mr. "Whiting had occasion to work out the results 

 of random matings of brothers and sisters, in connection with his 

 work at the Bussey Institution. He found that the amount of 

 heterozygosis was reduced one eighth in matings of the F 2 gen- 

 eration and from this concluded that the remaining heterozygosis 

 was reduced one eighth in each succeeding generation, so that in 

 the •nth generation the number of matings which would produce 

 at least some heterozygous offspring would be (7/8) He 

 showed these figures to Dr. East, who agreed with the general 

 conclusion (tendency toward homozygosis), but thought that the 

 ratio would not hold for offspring after the F 3 generation. Dr. 

 East, however, after a casual examination was not able to show 

 Mr. Whiting the fallacy in his work and did not go into the 

 matter further. 



In the American Naturalist for October, 1913, Dr. Raymond 

 Pearl criticized the extension of the conclusions for self-fertilized 

 plants to the animal kingdom. 4 He applied the figures of Pear- 

 son, 1904, 5 for random matings, which show that the relative 

 number of homozygotes and heterozygotes remains constant in 

 a population where all factors of fertility, virility and environ- 

 ment have the same effect upon each individual in each genera- 

 tion. Dr. Pearl's error, as he has since recognized, lies in the 

 fact that in the F 2 generation random mating involves only 

 brothers and sisters, while in all subsequent generations it also 

 involves other relationships. 



When I read Dr. Pearl's article in October I naturally won- 

 dered why there was such a difference of opinion between Dr. 

 East, Mr. Whiting and Dr. Pearl. Before finishing the article I 

 computed the amount of homozygosis in the F t generation as 

 per cent. ; in F 2 , 50 per cent. ; F 3 , 50 per cent. ; F 4 , 62.5 per cent., 

 and F E , 68.25 per cent. As soon as possible after that I figured 

 other generations until the heterozygosis would be reduced to 

 one half of one per cent, of the maximum of heterozygosis in the 



*East and Hayes, 1912, loc. cit. 



6 Phil. Trans. Hoy. Soc. (A), Vol. 203, pp. 59 and 60. 



