THAT BREED TRUE IN THE GROUSE LOCUSTS 479 

























The linkage of M and Z occurs on an average in three gametes out of 
a hundred by a female heterozygous for these factors. T may be linked 
_ with these in about three gametes out of a thousand produced by females. 
carrying M and Z linked on one, and T on the other of the pair of chro- 
mosomes. K may then be added to these in about one in a thousand ga- 
metes produced by females carrying M, Z and T linked on one, and K 
on the other of the pair of chromosomes. After M, Z, T and K are once 
4 linked, the next generation will bring individuals homozygous for all 
the factors for these dominant patterns. One is enabled to see by refe- 
rence to the Diagram of Factor Relations how a large number of true 
breeding complexes might be developed consisting of two, three, or 
four elementary patterns. If B, H, M and Y are not allelomorphic, or 
alternative, about which there is still uncertainty, much greater varie- 
ty and complexity could be attained. | 
Individuals with three linked factors for dominant patterns have of- 
ten been found in nature ,and there is no reason to doubt the existence 
of four or more linked. When once linked the tendency is to remain so, 
as the farthest apart of any of the factors so far studied, M to G or K, 
represents an average of less than 10 % of crossing over. 
Since the females of A. eurycephalus are parthenogenetic (Nabours 
19), often laying eggs that hatch without fertilization even when ma- 
ted, and such offspring are, with rare exceptions, females, and invaria- 
bly homozygous for all factors carried, a complex form would stand a 
good chance of perpetuation even without isolation. This would be es- 
pecially true if the linking of the factors should prove of benefit, a point 
however, on which there are as yet no data available. 
terns of this species in use in the experiments; five, Y, O, R, W and G, in addition 
to the four here used, having been reported (Nabours ’19). Over 450.000 reactions. 
of these factors in breeding show that they are in one series, or on one pair of 
chromosomes, and are in relation to each other as shown by the following Dia- 
gram of Factor Relations, with the distances approximated only. 


O 
BM di as 
Vu | W \G 
Z 
Diagram of Relations of Factors for Color Patterns in Apotettix eurycephalus 
Hancock: 
An extended account of the development of this diagram with the data is now 
ready for publication. ' 
