Abstract
The histological development of the eyes of Bar and wild type Drosophila melanogaster during the larval and pupal stages is described. The onset of morphological differentiation of the ommatidia of both Bar and wild type occurs between 48 and 72 hr. after hatching from the egg (temperature = 25° ± 0.2 °C). At all stages the developing ommatidia of Bar and wild type are the same. At no time was evidence of degenerating ommatidia found in any region of the Bar eye. The data are discussed in the light of several hypotheses that have been advanced to explain the development of the Bar eye.