viii HEREDITY 145 



fuzzy cottons have been evolved from primitive cottons 

 with entire fuzz by the loss of factors. The particular factor 

 lost has not been the same in certain strains of Egyptian 

 as in others, nor as in Hindi ; hence we obtain reversion in 

 some crosses, though not in others. No case of reversion 

 in inter-Egyptian crosses has yet been noted, but it is 

 quite conceivable. 



Colour of the seed fuzz. The presence and absence 

 of colour in the fuzz-hairs appear to form a Mendelian 

 pair. It is not easy to decide on the absence of colour, 

 since the colouring matter is unstable, and in some cases 

 fades very easily. There may be essential differences 

 between green and brown fuzz, but the former fades very 

 readily into the latter. 



The quantity of fuzz on the parent is not coupled with 

 colour. Thus, seeds which are practically naked, except 

 for a most minute tuft of coloured hairs at the tip, will 

 give rise, on crossing with white entire fuzz, to an F x 

 possessing green entire fuzz. It is interesting to note 

 that this phenomenon, together with the F 2 resulting, has 

 been described * as an instance of the failure of Mendel's 

 Law ; it was expected that " black seed " should form an 

 allelomorphic pair with " white seed." 



Distribution of lint on the seed, Parallel with the 

 seed fuzz distribution and colour, we find characters of lint 

 distribution and colour. 



The distribution of the lint is not easily recorded, there 

 being a large subjective error involved by the combing 

 which is required before it can be seen. Crosses of 

 " irregular "* with "regular" give a "regular" F 1; and 

 segregation certainly seems to occur. The most convincing 

 example of this was an F 3 from a "regular" F 2 plant. 

 The irregularly covered seeds were clearly defined, so that 

 the curve for weight of lint per seed showed a very 



* Cook, O. F. (1). 



