61 



An Experimental Estimation of the Theory of Ancestral 

 Contributions in Heredity. 



By A. D. Darbishire, Demonstrator of Zoology in the Koyal College of 



Science, London. 



(Communicated by J. Bretland Farmer, F.R.S. Received December 7, 1908, — 



Read February 11, 1909.) 



The experiments described in the following pages were undertaken with 

 the object of finding out if the proportions in which characters segregate in 

 the F 2 generation are affected by the distribution of those characters over 

 the parentage and ancestry of the forms crossed. To this end I crossed a 

 yellow pea with an extracted green in F 5 , and obtained a purely negative 

 result. The proportion of yellows and greens in the F 2 generation from this 

 cross did not differ sensibly from that obtaining in the F 2 generation from 

 a cross between a pure yellow and a pure green. The nature and result of 

 the experiment may be summarised in the following pedigree, in which the 

 two forms which I crossed are enclosed in brackets : — 



Y G 



Y 



Y 

 I 



[YxG] 



I 



Y 



/\ 



/ \ 



75-12 per 24-88 per 

 cent. cent.* 



Details of the Experiment. 



The Parent Forms. — (i) The Greens. 



The original cross which provided me with the extracted F 5 greens used in 

 my experiment was made by Mr. C. C. Hurst, and has been fully described 



* See Summary on p. 78. 



