156 HEREDITY AND ENVIRONMENT 



tations is possible. It seems probable, as 

 Boveri has shown, that different chromosomes 

 of the fertilized egg differ in hereditary po- 

 tencies, and where the number of chromosomes 

 is fairly large the number of possible combi- 

 nations of these chromosomes in the germ cells 

 becomes very great. In woman, where there 

 are probably 48 chromosomes, and, after 

 synapsis, 24 pairs of maternal and paternal 

 ones, the possible number of permutations 

 in the distribution of these chromosomes to 

 the different egg cells would be 2 24 , or 

 16,777,036, and the possible number of differ- 

 ent types of fertilized eggs or oosperms which 

 could be produced by a single pair of parents 

 would be ( 16,777,036) 2 , or approximately 

 three hundred thousand billions. But prob- 

 ably other things than chromosomes differ in 

 different germ cells, and it is by no means 

 certain that individual chromosomes are al- 

 ways composed of the same chromomeres, or 

 units of the next smaller order, and in view of 

 these possibilities it may well be that every hu- 

 man germ cell differs morphologically and 

 physiologically from every other one, in short 



