SOME NEW PRINCIPLES 245 



absolutely independent of one another. A pea which 

 is yellow is not for that reason any more or less likely 

 to be round. At the other end of the series there 

 are two such characters as the purpleness of the 

 flower and the purpleness of the axil, the angle 

 where the flower-stalk joins the main stem. These 

 two characters cannot be separated by hybridising ; 

 it is impossible to breed a purple -flowered pea with a 

 green axil, or a purple-axilled one with a white 

 flower. The two characters are apparently indis- 

 solubly connected. The comment may be made, on 

 this, that they are not two characters, but one. And 

 my answer to this is that I have no objection to 

 expressing the fact that two characters are indis- 

 solubly associated by calling them one character, 

 except that it is better to refer to two apparently 

 indissociable characters which we can conceive of as 

 being separated, or desire to be separated, as two 

 characters, partly because it may turn out that they 

 are separable by as yet undiscovered methods, and 

 partly because by naming them one character we 

 renounce the attempt to separate them. 



Between these two extremes of association there 

 are intermediate forms. A great deal of work has 

 been done in the hope of interpreting the various 

 types of association on Mendelian lines. These, 

 however, do not concern us here, and it will suffice 

 to describe a single instance of two characters belong- 

 ing to distinct pairs which are imperfectly associated 

 together. One of these characters is purpleness of 

 flower in the culinary pea ; the other is the occurrence 



