THE MECHANISM OF HEREDITY 37 



of chromosomes (Fig. 24) and seven independent pairs 

 of Mendelian characters, according to White. In Indian 

 com there are ten to twelve (I) pairs of chromosomes, 

 and several groups of linked genes have been detected. In 

 the snapdragon, with sixteen pairs of chromosomes, the 

 number of independent genes approaches the number of 

 the chromosomes. In other animals and plants, also, 

 linked genes have been reported, but as yet this number 

 is small in comparison with the chromosome numbers. 



Edible Pea Sweet Pea^ 



India.!! Cort) 



Fig. 24. 

 The reduced number of chromosomes in the edible pea (n^7), 

 sweet pea (n^7), and Indian corn (n^lO or ]2?). 



The further fact that, to date, no case is kno^vn where 

 there are more independently assorting pairs than there 

 are pairs of chromosomes is further evidence, as far as it 

 goes, in favor of the view that the linkage groups and 

 the chromosomes correspond in number. 



The Integrity and Continuity of the Chromosomes. 



The integrity of the chromosomes, or their continuity 

 from one cell generation to the next, is also essential for 



