Morgan mated a wild-type
red-eyed
female with a mutant
white-eyed
male. The F1 offspring all had red eyes.
Morgan then bred the F1 flies to produce the F2 generation.
The F2 showed a typical Mendelian 3:1 phenotype ratio of red:white eyes.
However, all females had red eyes. Half the males had white eyes, and half had red eyes.