HEREDITY 



515 



other is extremely delicate, as a light shade of blue, easily lost 

 in the red, or a lightness of foliage, easily obscured by a 

 heavy stem. 1 Now, under circumstances such as these, the less 

 noticeable, or " recessive," characters will be visible only in the 

 individuals that are pure recessives, all others being dominated by 

 the more pronounced character. Thus, if D stands for dominant 

 (red petal or strong stem) and r for recessive (light-blue petal 

 or delicate foliage), then the actual distribution would be Z^-f- 

 2 Dr + r 2 as before ; but in this distribution three out of four 

 individuals would be distinguished by the dominant character, 

 while the less assertive, the recessive character, would be ob- 

 scured except in the 25 per cent in which it exists unmixed 

 with the dominant. Hence an individual showing a recessive 

 character may be known at once to be pure, but we cannot 

 tell by looking at individuals showing the dominant character, 

 which are pure and which are mixed. We know, in fact, that 

 we have both forms in the proportion of I to 2, but in a case 

 of this kind 75 per cent would appear to be dominant, while only 

 25 per cent would appear to be recessives. In reality, 25 per 

 cent &TQ pure dominants, the other 50 per cent being apparently 

 dominants, but actually mixed, a fact that immediately be- 

 comes evident when they are bred among themselves, as they 

 at once give rise to the characteristic distribution, with the 

 proper 25 percent of pure recessives. 



Inasmuch as few pairs of characters are equally balanced and 

 equally able to make themselves evident, it is generally true 

 that any generation from crossed parentage will show 75 per 

 cent dominant (really 25 pure and 50 mixed) and 25 per cent 

 recessive, instead of the typical 25, 50, and 25 that would 

 appear if the characters were equally evident and equally 

 assertive. 



Distinction between characters and individuals. The reader 

 will be misled if he takes individuals into consideration here 

 instead of characters. The entire discussion applies to charac- 

 ters taken singly, and when we say of an individual arising from 

 hybrid parents that he will " breed pure," we mean only as to 



1 It is clear that only characters that are " mutually exclusive " can be used in 

 experimenting on or illustrating this subject 



