DISTRIBUTION OF THE CHROMOSOMES 147 



cell, or it may even be torn apart, as if by spindle 

 fibers from opposite poles. Consequently less than 

 half of the gametes (at least the sperm, for gameto- 

 genesis was not studied in the female organs) receive 

 the extra chromosome. The proportion varies greatly 

 in different individuals. This conforms with the 

 genetic result that lata individuals, crossed to la- 

 marckiana, give varying proportions of lata offspring 

 but never produce offspring more than half of which 

 are lata. 



In Primula, a striking case of correspondence be- 

 tween abnormal genetic and chromosome phenomena 

 has been found, that appears strongly in favor of the 

 chromosome hypothesis, although the discoverer, 

 Gregory, has hesitated to draw this conclusion. Two 

 giant races of the primula (P. sinensis) were found to 

 have twice the number of chromosomes character- 

 istic of other domesticated races. The breeding ex- 

 periments with these plants show that they also have 

 a double set of factors as compared with the same 

 factors in ordinary primulas. While in ordinary plants 

 each chromosome is double and, therefore, each factor 

 is represented twice, for instance by A and A, in the 

 giants there are four like chromosomes, hence four 

 factors AAAA. If the giant race contains some fac- 

 tors already mutated, such as A\ the giant might con- 

 tain one, two, three, or four of the mutant factors 

 A^ Such plants would be AAAA^ or AAA^A^ or 

 AA^A^A^ or A^A^A^A^ As stated above, the breed- 

 ing work shows that there is a quadruple set of 

 factors, but the evidence is as yet insufficient to de- 



