188 MENDELISM 
Let us consider the external appearance of these 
various types in the particular example before us. 
Nine of the above sixteen terms include A and B, 
and are therefore smooth yellow in appearance. (We 
need not stop to consider whether a or b or both are 
present in addition, since these are recessive.) 
Three terms include A and 0, B being absent. These, 
therefore, appear wrinkled yellow. 
Three include a and B, A being absent. These, 
therefore, appear smooth white. 
One contains 4 and 0 only, and is, therefore, wrinkled 
white. 
With regard to internal constitution : 
The nine individuals of appearance AB include the 
following types : 
One pure, ABAB, breeding true to the smooth 
yellow type on self-fertilization. 
Two ABAD, heterozygous in respect of the 
pair B-b, but pure yellow. 
Two ABaB, heterozygous in respect of A-a, 
but pure smooth. 
Four ABab, heterozygous in respect of both 
pairs of characters. 
The three individuals of appearance Ab include the 
following types : 
One pure, AbAd, breeding true to the (new) 
wrinkled yellow type. 
Two Abad, giving both wrinkled yellow and 
wrinkled white. 
