HIS THEORY OF HEREDITY 119 



happen when these two are crossed together ? As a 

 matter of fact we find that the red is dominant. 

 But in the second generation we have nine red, 

 three red with cream, three white and one cream 

 as before. What is the white ? White was not put 

 in. Apparently we have produced it de novo an 

 albino by crossing two coloured forms : cream 

 was a corpuscle colour, red was a sap colour, but 

 the white have colourless corpuscles floating in 

 colourless sap. It is evident what has happened. 

 Which are the factors which segregate in the form- 

 ation of the germ cells ? They are (a) red sap 

 from colourless sap, and (b) white corpuscles from 

 yellow corpuscles ; so that when the possible com- 

 binations of those two pairs of characters are made, 

 colourless corpuscles may coincide with colourless 

 sap, and a white flower is the result. I think the 

 answer is quite clear." * 



Sufficient has now been said to show what 

 Mendel's law is and the important results which 

 may flow from it ; but it would not be fair to con- 

 clude without stating that there is still an im- 

 portant body of biologists who refuse to believe 

 in the truth of the theory, and severe, even acrimo- 

 nious, contests have been waged between the 

 upholders and the deniers of Mendelian views. 

 The chief opponent was the late Professor Weldon 

 of Oxford. To discuss the exact points at issue 

 would occupy more space than can be afforded in 

 an article of this kind, of which the main object 

 is to describe Mendel's theories and some recent 



* British Medical Journal, ut supra. 



