128 
HEREDITY OF THE BLACK CROSSED WITH THE NINE-SPOTTED 
PHASE. 
In considering these breeding experiments in detail let us 
first take up the results of the crosses of the black with the 
nine-spotted phase. Pairs No. 16 and 17 consisted of black 
females reared from female No. 5 mated with nine-spotted males 
reared respectively from the nine-spotted pairs Nos. 6 and 9. 
From female No. 16, 6 nine-spotted beetles, and from female 
No. 17, 19 beetles of the same form were reared without either 
normal or black offspring. The reciprocal cross No. 35 had 
similar ancestry, the female having been reared from the nine- 
spotted pair No. 27, the black male from the F: generation 
of female No. 17. This crossing gave twenty-three nine-spotted 
beetles.* We see, therefore, that the nine-spotted phase is 
dominant over the black. 
If the cross of black and nine-spotted forms is truly Men- 
delian in inheritance, as indicated by the dominance of the 
nine-spotted form over the black, the mating together of the 
nine-spotted offspring of this cross should produce in the fol- 
lowing generation both nine-spotted and black forms in the 
proportion of 3 to 1. Consequently, three matings were made 
of the offspring of pairs No. 16 and 17, numbered respectively 
19, 20, and 22. The results are conveniently given in tabular 
form. 
Female Male Phase of 
Pair No. from from parents Character of offspring 
ig No. 17 No. 17 Nine-spotted 15 nine-spotted, 5 black 
20 No. 17 No. 17 Nine-spotted 3 nine-spotted, 2 black 
22 No. 17 No. 17 Nine-spotted 4 nine-spotted, 1 black 
Totals 22 nine-spotted, 8 black 
We see, therefore, that the black phase reappeared in IF. 
generation approximately in the correct Mendelian proportion. 

+ Towards the end of this breeding experiment one normal and one 
black beetle issued from two lots of larvae reared to maturity, but there 
is considerable probability that these had gotten mixed in by mistake. 
If large numbers of larvae are handled at the same time, a small per- 
centage of mixture of the different lots must be expected to occur occa- 
sionally, even if great care is taken to prevent this mishap. 
