No. 637] FIBST GENERATION HY:^IDS 



133 



point of the class. The result of this change in plotting 

 is to increase the range of sizes included in the higher 

 classes and consequently to raise the mode. 



In conclusion it would seem, therefore, that the as- 

 sumption of linkage, while perhaps not improbable, is 

 superfliious so far as the explanation of heterosis is con- 

 cerned, since neither of the objections which it was 

 framed to meet have foundation in fact. 



It is, perhaps, too much to assert that the suppression 

 of deleterious recessive characters completely explains 

 heterosis or that the reappearance of these characters is 

 the only factor in the decline in vigor that follows in- 

 breeding, but the behavior of maize is in full accord with 

 this explanation. 



LITERATURE CITED 



1919. Uroleptus moUUs Eugelm. II. Renewal of Vitality through- 

 Conjugation. Jour. Experimental Zoology, 29: 121-156, Oct. 

 5, 1919. 

 E. M., and Jones, D. F. 



I. Inbreeding and Outhreeding. 

 , E. A., and East, E. M. 



!. The Quantitative Characters in :\[aize. Xcbr. Exp. Sta. Re- 

 search Bull. No. 2. 



s, D. F. 



1917. Dominance of Linked Factors as a Means of Accounting for 

 Heterosis. Genetics, 2: 466-479, Sept., 1917. 

 The Effects of Inbreeding and Crossbreeding upon Development. 

 Conn. Agric. Exp. Sta. Bull. 207, Sept., 1918. 

 , and Pellew, C. 



The Mode of Inheritance of Stature and the Time of Flowering 

 in Peas. Joxir. of Genetics, 1: 47-56, Nov. IS, 1910. 



