24 MENDELIAN SEGREGATION 
Chance meeting between these will give the results 
shown in the next diagram (Fig. 12). 
In the table (Fig. 12) the four kinds of eggs are 
represented at the head of the four vertical columns, 
and the four kinds of spermatozoa at the left of each 
horizontal row. In the squares the combination of 
each kind of sperm with each kind of egg is repre- 
sented, giving the ratio of 9 long gray: 3 vestigial 
gray: 3 long ebony: 1 vestigial ebony. 
The F, expectation may, of course, be derived more 
directly as follows: There will be 3 long to 1 ves- 
tigial. These longs will be both gray and ebony in 
the ratio again of 3 to 1; hence 9 long gray to 3 long 
ebony. Correspondingly, the vestigials will be both 
gray and ebony, in the ratio of 3 to 1; hence 3 
vestigial gray to 1 vestigial ebony. The result is the 
same as before. 
If one of two independent pairs of characters is 
sex linked, the same scheme holds in those cases where 
the recessive sex linked character enters through the 
grandfather, but the ratio is different when the re- 
cessive sex linked character enters through the 
grandmother (viz.,3:3:1:1), as is to be expected 
from the mode of inheritance of white eyes taken 
alone ;! and here, too, the result conforms fully to the 
chromosome scheme. 
Three factors can be worked out by means of the 
1For example, taking white and red alone the ratio of the F. is 
1:1. But among the reds the ratio of gray to ebony will be 3:1 and 
. among the whites will be 3:1. Hence the result 3 red gray, 1 red ebony, 
3 white gray, 1 white ebony. 
