The Cellular Basis 171 



such as a spermatozoon, to allow for all these differences? Mie- 

 scher has shown that a molecule of albumin with 40 carbon atoms 

 may have as many as one billion stereo-isomers, and in protoplasm 

 there are many kinds of albumin and other proteins, some with 

 probably more than 700 carbon atoms- In such a complex sub- 

 stance as protoplasm the possible variations in molecular con- 

 stitution must be well nigh infinite, and it can not be objected on 

 this ground that it is chemically and physically impossible to 

 have as many varieties of germ cells as there are different kinds 

 of individuals in the world. 



Permutations of Chromosomes. Even with regard to morpho- 

 logical elements which may be seen with the microscope it can be 

 shown that an enormous number of permutations is possible (Fig. 

 58). It seems probable, as Boveri has shown, that different 

 chromosomes of the fertilized egg differ in hereditary potencies, 

 and where the number of chromosomes is fairly large the number 

 of possible combinations 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 pa- 

 ternal ones, the possible number of permutations in the distribu- 

 tion of these chromosomes to the different egg cells would be 2 24 , 

 or 16,777,216, and the possible number of different combinations 

 of fertilized eggs or oosperms which could be produced by a single 

 pair of parents would be (16,777,21 6) 2 , or approximately three 

 hundred thousand billions. f But probably other things than chro- 

 mosomes differ in different germ cells, and it is by no means cer- 

 tain that individual chromosomes are always composed of the same 

 chromomeres, or units of the next smaller order, and in view of 

 these possibilities it may well be that every human germ cell 

 differs morphologically and physiologically from every other 

 one, in short that every oosperm and every individual which de- 

 velops from it is absolutely unique. 



Significance of Sexual Reproduction. Indeed the production 

 of unique individuals seems to be the chief purpose and result of 



* See pp. 161-163. 



t Excluding duplications there would be 3 24 different genotypes and 2 24 

 different phenotypes, assuming that chromosomes always preserve their 

 identity and that dominance is always complete. 



