


AS CAUSE OF THE APPARENT CONSTANCY OF THE MUTANT „SPREAD. 333 
Of these types only the two lastmentioned are viable, as the 
former are homozygotic in the lethal factors Spr and vit respec- 
tively. Of the two viable types only the New normals are pheno- 
typically conspicuous, as the New Spread type quite resembles 
Old Spread. 
_ Normal-winged individuals that suddenly arose in Spread cultures 
thus should constantly be of the New normal type, and I have 
made some ‘crossing experiments to examine this question. 
VIII. Cross-over X Old Spread 
(normal) 


Spread Normal 




EEN KEN oe 
ERW LS 8 9 7 7 
XK 94 en BRE NA LI 
x K 196 a oe 7 2 
x K 230 68 79 ie ESO 798 
K 242 e102 12210 9 3 
K 244 RTS 4 5 


|118 | 144 | 93 | 56 
Found in alla. à 262 149 



Nee con 137 
As was expected, the two types occur in a number which is 
near the relation 2 Spread: 1 normal which shows that the suddenly 
arising normal-winged individuals are not Old normals but contain 
the lethal factor, just as is the case with the New normals produced 
by crossing. Considering the number the relation 262: 149 is in 
fair accordance with what was expected, but a fact that is rather 
peculiar is the unequal frequency of females and males within the 
two categories. This inequality may possibly be due to a mere 
accident, as the material is not very comprehensive. However, in 
the very nature of things it is difficult to procure a great material 
of cross-over individuals when the linkage is very strong, and 
