306 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 



only A and a can pair together, B and b, and C and c, but each pair 

 operates independently of the other so that in the ensuing i-eduction 

 division either member of a pair may get into a cell with either member 

 of the other pairs. That is, the line up for division at a given reduc- 

 tion might be any one of the following, 



L L^ n^ T> • This would yield the following eight kinds of 

 abc abC aBC aBc o o 



gametes, ABC, abc, ABc, abC, Abc, aBC, AbC, aBc, each bearing one 

 of each kind of chromosome required to cover the entire field of 

 characters necessary to a complete organism. And since each sex 

 would be equally likely to have these eight types of gametes and any 

 one of the eight in one indi-\ddual might meet any one of the eight of 

 the other, the possible number of combinations in the production of a 

 new individual from such germ-cells would be 8X8, or 64. With 

 the larger numbers of chromosomes which exist in most animals it is 

 readily seen that the number of possible combinations becomes very 

 great. Thus any individual of a species with twenty chromosomes 

 — and many animals, including man, have more — would have ten 

 pairs at the reduction period and could therefore form (2)'°, or 1,024 

 different gametes in each sex. And since any one of these in one 

 sex would have an equal chance of meeting with any one in the oppo- 

 site sex, the total number of possible different zygotes that might be 

 produced would be (1,024)^, or 1,048,576. Sex, therefore, through 

 recombinations of ancestral materials, undoubtedly means, among 

 other things, the production of great diversity in offspring. 



