35 Mendel's Experiments 



A l a + A z a+... and so would it be with the corresponding 

 colouring of the seed-coats*. According to the above 

 assumption, each of these hybrid colour unions would 

 be independent, and would consequently develop quite 

 independently from the others. It is then easily seen 

 that from the combination of the separate developmental 

 series a complete colour-series must result. If, for instance, 

 A=A 1 + A Z , then the hybrids A^a and A. z a form the 

 developmental series 



The members of this series can enter into nine different 

 combinations, and each of these denotes another colour 



1 A,A 2 2 A,aA, i A n _a 



2 A^A^a 4 A^aA^a 2 A^aa 

 i A^a 2 A^aa i aa. 



The figures prescribed for the separate combinations 

 also indicate how many plants with the corresponding 

 colouring belong to the series. Since the total is sixteen, 

 the whole of the colours are on the average distributed 

 over each sixteen plants, but, as the series itself indicates, 

 in unequal proportions. 



Should the colour development really happen in this 

 way, we could offer an explanation of the case above 

 described, viz. that the white flowers and seed-coat colour 

 only appeared once among thirty-one plants of the first 

 generation. This colouring appears only once in the series, 

 and could therefore also only be developed once in the 

 average in each sixteen, and with three colour characters 

 only once even in sixty-four plants. 



It must, nevertheless, not be forgotten that the explana- 

 tion here attempted is based on a mere hypothesis, only 

 supported by the very imperfect result of the experiment 

 just described. It would, however, be well worth while to 

 follow up the development of colour in hybrids by similar 



* [As it fails to take account of factors introduced by the albino this 

 representation is imperfect. It is however interesting to know that Mendel 

 realized the fact of the existence of compound characters, and that the 

 rarity of the white recessives was a consequence of this resolution.] 



