08 



THE AMEBIC AN NATURALIST [Vol. XLVIII 



In a recent paper' ('in-gory reports ;i very interesting case in 

 which two different races of Primulas suddenly gave rise to giant 

 tetraploid forms, having double the usual number of chromo- 

 somes, and apparently having the factors doubled also (individu- 

 ally), for this was true of all the factors which could be followed 

 in his hybridization experiments. It is important to know how 

 segregation will take place in such individuals, as there are four 

 allelomorphs of each gene present. 



Let us suppose that a tetraploid form pure for the dominant 

 factor A ^ and therefore of composition ~ jj^j is crossed with a 

 pure recessive giant (~*~^- Gametes AA and aa will meet in 

 fertilization, forming the hybrid — — (the maternally derived 

 genes are represented on one line, say the upper, the paternally 

 derived genes on the other line). 



Now, if this were an ordinary ease of "multiple factors" 2 in a 

 diploid organism, although the two dominant factors, which we 

 may again call A's, may produce the same effect upon the organ- 

 ism, yet they are not interchangeable, and the same is true of the 



the 



disl 



redity, we would say that A and a always lay opposed to 

 each other, in homologous chromosomes, on the spindle of the 

 reduction division, as did also A 1 and a 1 , but neither A nor a 

 lay in chromosomes homologous to those of either A 1 or a 1 , 

 and assorted independently of them. The line-up of factors on 

 the spindle in the reduction division in this case would be 

 equally likely to be - or — depending merely upon which 



