SEX AND HEREDITY 



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one white ; line 4 one of the blacks (the pure one) of 

 line 3 produces only blacks, the other two blacks each 

 produce three blacks (one pure and two hybrid) and one 

 white, as before. Whites, of course, produce nothing 

 but whites. 



This is obviously the same as the case of the snap- 

 dragon, reading red for black. It will also be appreciated 

 that the way in which the contrasted characteristics of 

 the parents behave in the body of the hybrid, blending 

 or otherwise is a purely subsidiary point, which does 

 not in any way affect the important matter of their 

 separation in the hybrid's gametes. 



Although a case of blending characteristics has been 

 chosen from the animal kingdom, and non-blending ones 

 from the vegetable kingdom, it must not be supposed 

 that these two types of inheritance are peculiar to animals 

 and plants respectively. On the contrary, experiments 

 on a very large number of characteristics colours, sizes, 

 shapes, etc., have shown that both kinds of inheritance 

 are found in both kingdoms, animals and plants exhibiting 

 an extraordinary similarity in the phenomena of heredity, 

 which can only mean that these are dependent upon the 

 most fundamental properties of living matter. 



On a first consideration it would appear, having regard 

 to our own experience of inheritance in man, that Mendel's 

 law has a limited application. This is not the case, however, 

 and it is conceivable that ultimately all inheritance will 

 be shown to be of this type, it being merely the conse- 

 quence of the -hereditary material being composed of 

 small units. Though here we are entering speculative 

 regions, where we are far from reaching general agreement 

 amongst biologists, it may be explained that it is supposed 

 that the colour of the feathers (for example) is dependent 



