88 MENDELISM chap. 



hitherto we have not been able to decide why this 

 should be so. 



Nor for the present can we suggest why certain 

 factors should be linked together in the peculiar 

 way that we have reason to suppose that they are 

 during the process of the formation of the gametes. 

 Nevertheless the phenomena are very definite, and it 

 is not unlikely that a further study of them may 

 throw important light on the architecture of the 

 living cell. 



APPENDIX TO CHAPTER IX 



As it is possible that some readers may care, in spite of 

 its complexity, to enter rather more fully into the peculiar 

 phenomenon of the coupling of characters, I have brought 

 together some further data in this Appendix. In the case 

 we have already considered, where the factors for blue 

 colour and long pollen are concerned, we have been led to 

 suppose that the gametes produced by the heterozygous 

 plant are of the nature 7 BL : i Bl:\ bZ:"] bl. Such a 

 series of ova fertilised by a similar series of pollen 

 grains will give a • generation of the following com- 

 position : — 



49 BBLL + 7 BBLI+ 7 BbLL + 49 BbLl 



+ 7 BBLI+ 7 BbLL + BbLl 



+ BbLl 



+ ^q BbLl 



• , ' 



177 purple, long 



+ BBII+7 Bbll+bbLL + 7 bbLl+^c, bbll 

 + 7 Bbl l + 7 bbLl 



15 purple, 15 red, 49 red, 



round long round 



and as this theoretical result fits closely with the actual 

 figures obtained by experiment we have reason for 



