220 R. RUGGLES GATES. 



tilization continues in this case throughout the ontogeny, though 

 this is not true for all organisms. Otherwise it would be necessary 

 to assume that when a plant in a 3:1 family gives rise to a 15:1 

 family all its germ cells have simultaneously undergone a mis- 

 mating of the chromosome pairs during meiosis, a highly im- 

 probable event. 



In the F 2 and F 3 hybrids of CE. rubricalyx and CE. grandiflora, 

 in addition to 3:1 and 15:1 ratios, 2:1, 4:1 and 5:1 ratios occur. 

 The 5:1 ratios at least seem to be significant, indicating that 

 R and r gametes are regularly being produced in the ratio 5:3, 

 or that a certain amount of re-grouping of the R chromosomes 

 is regularly occurring during meiosis. 



