Regeneration, post-embryonic induction and cellular interaction in the eye of Periplaneta americana.

1. The eye grows by the addition of new ommatidia rather than by an increase in size of existing ones. 2. New ommatidia develop as a result of induction of epidermal cells by functional ommatidia. 3. The eye has great regenerative ability, but following removal of the entire eye and the growth zone that surround it regeneration does not occur. 4. Transplanted eye cells or epidermal cells from normal-eyed or from lavender-eyed mutants resulted in the development of normal eye pigmentation in a mutant that lacked any pigmentation in the eye. Only the eye to which the graft had been made developed pigments. The development of pigments was a result of tissue contact, not of a blood-borne factor. 5. When epidermal tissues from the prothorax of normal-eyed roaches were placed above the developing eye of a mutant with no pigment in the eye they were eventually incorporated into the eye as it grew. When these cells became eye cells, normal eye pigments were synthesized. 6. Growth of the eye is by a constant recruitment of epidermal cells that express their own genetic capability when they become eye cells.