The Role of the Chromosomes 207 



In this way, and in this way only, may bs reasonably 

 explained the results of Mendelian inheritance, in which the 

 characters of the parents are shuffled, and dealt to the off- 

 spring like the cards in a pack. Mother Nature is an invet- 

 erate gambler, and every living thing a pack of cards. 



But is such a scheme of chromosome distribution adequate 

 to account for the infinitude of characters shown by so com- 

 plex an organism as man, no two individuals of whom are 

 ever exactly alike, with the possible exception of the very 

 rare cases of identical twins? Chromosome counts in man 

 are hard to make as may be readily understood from the 

 difficulty of securing fresh and undiseased material for micro- 

 scopic study. If, as seems probable however the number is 

 48, which in maturation unite to form 24 pairs, then the 

 number of possible arrangements of these chromosomes, deter- 

 mining their distribution to the different germ cells, is 2 24 or 

 16,776,116, and the number of possible combinations re- 

 sulting from the union of the germ cells in fertilization is 

 (16,776,116) 2 or about 280,000,000,000,000. This calculation 

 is based on the assumption that each chromosome carries but 

 a single determiner. It is highly probable however as we 

 shall see later, that each chromosome carries a large number 

 of determiners, and that these are mutually interchangeable 

 between the members of each pair of chromosomes. Allowing 

 ten determiners to every chromosome, which is probably a mod- 

 erate estimate, and the last stated figures become about 3,- 



ooo,ooo,ooo,ooo,ooo,ooo,coo,ooo,ooo,ooo,ooo,ooo,ooo,roo,oco,- 



0)0,000,000,000,000,000,000,000,000,000,000, 000,000,OCO,000,~ 

 000,000,000,000,1000,000,000,000,000,000,000,000,000,000,000- 

 000,000,000. 2 If any reader cares to form a mental picture 

 of this number he is welcome to try ! 



It is by no means certain however that the determiner is a 

 fixed and unchangeable unit. In fact, the very reverse is 

 undoubtedly the case. Chemical analysis of the exceedingly 

 complex components of the cell is very difficult, and the results 

 vary widely. All observers are agreed however as to the great 

 complexity of protoplasm. According to Miescher, nuclein, 

 which forms the major part at least of the chromosome, has 

 the formula C 29 H 49 N 9 P 3 2 . Now there are certain sub- 

 stances, especially among the compounds of carbon, that 

 wonderfully kaleidoscopic element, which analysis shows to 

 have the same structure, but which nevertheless exhibit dif- 

 ferent properties. These differences are explained on the 

 assumption that while the molecules of these substances con- 



2 Computed by Professor E. F. Chandler, of the University of North 

 Dakota. Even should the above figure be greatly reduced by linkage it 

 would still be so large as to be absolutely incomprehensible, 



