2 20 POPULAR SCIENCE MONTHLY. 



at least, is still very strongly of the belief that the investigator of 

 reproductive cells holds the keys of evolution, and he even finds it 

 remarkable that a general cytological explanation of these 'principles 

 of inheritance' was not suggested before. According to Professor 

 Wilson the facts discovered by Mendel, that in some hybrids, characters 

 of the parents are not permanently combined, are explainable by the 

 'normal phenomena of maturation,' that is, if we admit that 'indi- 

 vidual chromosomes stand in definite relation to transmissible char- 

 acters,' and that the 'reducing division' by which the reproductive 

 cells are formed 'leads to the separation of paternal and maternal 

 elements and their ultimate isolation as separate germ-cells.' This 

 would be important if true, but the Mendelian facts are unable to 

 accept this proffered support of cytological theory, because they have 

 already demonstrated its falsity. 



The commonly accepted view of organic descent may be illustrated 

 by a simple diagram which indicates that a single individual may 



A B C D 



\ / \ / 



\ / \ / 



\y 



\ 



I 



ABCD 



inherit characters from all four of its grandparents. Professor Wil- 

 son's explanation of Mendel's law would deny this possibility, and 

 would limit the descent of all individuals to two grandparents, so that, 

 the form of our family tree would be completely altered. 



A EC n 



\ 



\ 



