1 5 6 
GENETIC STUDIES ON THE SILKWORM 
PQYPqY iPQY: [PqY . Class IV 
PQYPQy iPQYrrPQyJ all normal yellow 
PQYPQy i PQY: iPQy 
PQYPqY i PQY: I PqY 
The results in subsequent generations can likewise be explained. All of the four 
classes given above were actually observed. 
B,C) F 3 normal white and plain yellow derived from the cross P&yPUy 
x PqYPqY were also not uniform in respect to the genetic constitution, some 
were homozygous, but others were heterozygous for one of the two allelo- 
morphs under consideration. 
F 2 normal white paired inter sc. 
F., matings 
Males 
Zygotes Gametes 
PQyPQy 
PQyPQy 
PQyPqy 
PQy 
PQy 
I PQy : iPqy 
Zygotes 
PQyPQy 
PQyPqy 
PQyPQy 
PQyPqy iPQy : iPqy PQyPqy iPQy = iPqy 
F a plain yellow paired inter sc. 
PqYPqY PqY PqYPqY PqY 
PqYPqY PqY PqYPqy i Pq Y : iPqy 
PqYPqy ]PqY : Pqy PqYPqY PqY 
PqYPqy i PqY : I Pqy PqYPqy iPqY : iPqy 
F 3 families 
Class V 
all normal white 
Class VI 
3 normal white 
I plain white 
Class VII 
all plain yellow 
Class VIII 
3 plain yellow 
I plain white 
The frequency of each class may be calculated as follows : — 
A) Frequency of the occurrence of the various families in the offspring 
of normal yellow in the Class I lot of any generation. 
Male Female 
6 PQyPqY x 6 PQyPqY 36 giving rise to Class I 
6 PQyPqY x 1 PQYPQy 61 
1 PQYPQy x 1 PQYPQy 1L.13 giving rise to Class II 
1 PQYPQy x 6 PQyPqY 6] 
