350 EXPERIMENTAL STUDY OF INHERITANCE 



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

 are represented by italics and capitals.) 



RY 



RY(ag) 



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

 100 of each): 



(1) 100 RYJ /-RY 100 



(2) 100 Rg I which in inbreeding unite with four similar J Rg 100 



(3) 100 aY | kinds jaY 100 



(4) 100 ag J [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) 



25 Rg x 25 RY = 25 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) 



(i) 

 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) 



= loo RY 



(3) 



25 aY x 25 RY = 25 RY (a) 

 25 aY x 25 Rg = 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 + 



- 50 RY + 50 aY 25 aY + 25 ag 



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 -t- i 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 



