350 EXPERIMENTAL STUDY OF INHERITANCE 



angular and Yellow, some angular and green. (The dominants 

 are represented by italics and capitals.) 



RY 



(i) ioo RY 



(2) 100 Rg 



(3) 100 aY 



(4) 100 ag 



which in inbreeding unite with four similar 

 kinds ........ 



RY(ag) 



Suppose the germ-cells segregate into the four possible kinds (say 

 100 of each) : 



RY 100 



Rg 100 



aY 100 



ag 100 



What are the possible combinations (it being understood that 



form and colour represent a pair of characters — i.e. RR, Ra, etc., 



are impossible). 



(2) 

 25Rgx 25RY=2 5 RY(g) 



25 Rg x 25 Rg = 25 Rg 



25 Rg x 25 aY = 25 RY (ag) 



25 Rg x 25 ag = 25 Rg (a) 



(0 

 25 RY x 25 RY = 25 RY 



25 RY x 25 Rg = 25 RY (g) 



25 RY x 25 aY = 25 RY (a) 



25 RY x 25 ag = 25 RY (ag) 



= 100 RY 



(3) 



25 aY x 25 RY = 25 RY (a) 

 25 aY x 25 Eg = 25 RY (ag) 

 25 aY x 25 aY = 25 aY 

 25 aY x 25 ag = 25 aY (g) 



= 50 RY + 50 Rg 



(4) 



25 ag x 25 RY - 25 RY (ag) 

 25 ag x 25 Rg = 25 Rg (a) 

 25 ag x 25 aY = 25 aY(g) 

 25 ag x 25 ag = 25 ag 



= 25 RY + 25 Rg + 

 25 aY + 25 ag 



= 50 RY + 50 aY 



The characters in brackets may be disregarded, since they behave as 

 recessives to their correspondents. Thus the total is — 



225 RY + 75 Rg + 75 aY + 25 ag 

 or 9 RY + 3 Rg + 3 aY -r 1 ag 



This actually corresponds with results obtained. 



In illustration of the crossing of forms with two pairs of con- 

 trasted characters, let us take one worked out by Toyama, 

 concerning two races of silk-moths. The one had white unstriped 

 caterpillars and yellow cocoons ; the other had banded cater- 

 pillars and white cocoons. Yellow is dominant over white, and 

 striped over unstriped. Thus all the hybrids (F) had striped 



