No. 531] GENOTYPE CONCEPTION OF HEREDITY 145 



fluent. So the differences between the phenotype-curves 

 may vary considerably or may even vanish entirely. 

 These experiences agree with numerous observations of 

 Wesenberg Lund as to the Daphnias in the Danish lakes, 

 and there is no doubt as to their correctness. 



But when Woltereck thinks that these facts are in- 

 consistent with the existence of constant differences be- 

 tween the genotypes, he shows himself to have totally 

 misunderstood the question! Of course the phenntupc* 

 of the special characters, i. e., the reactions of the geno- 

 typical constituents, may under different conditions ex- 

 hibit all possible forms of transition or transgression 

 — this has nothing at all to do with constancy or incon- 

 stancy of genotypical differences. 



Every student of genetics ought to know this; some 

 few examples may suffice to enforce it : Temperature has 

 great influence upon the intensity of color in flowers ; all 

 shades of intensity from saturated reddish-blue to pure 

 white may be observed with different temperatures in 

 lilac flowers of the " colored" varieties. Such pure 

 white flowering individuals are — as to color — pheno- 

 typically not distinguishable from genotypical ly pure 

 "white" varieties. Nobody will assume that there 

 should be genotypical transitions here! Pure lines of 

 beans may in one year be different in size. e. g., the 

 average of the line A exceeding that of B. In another 

 year B may exceed A, or their average sizes may be 

 practically identical. Differences of soil may produce 

 something similar, and it is well known to breeders that 

 some strains of wheat yield relatively much better than 

 others on rich soil, while the reverse is realized on 

 poorer soils. In four subsequent years two pure lines of 

 barley, both characterized by a considerable degree of 

 disposition to produce vacant spikelets (aborted grains) 

 in the heads, presented the phenotypes here indicated in 

 percentages of such vacancies. 



Pure line L: 30 33 27 29 

 Pure line G: 5 45 3 28 



