The influence of the quantity and quality of chromosomal material on the size of the cells in drosophila melanogaster.

1. The small bristles on the surface of the wing ofDrosophila correspond each to a single cell. This fact makes possible the measurement of the size of the cells by counting the number of bristles within a known area of the wing surface. 2. Comparison of the cell size in male, female, superfemale, supermale, intersex and triploid female showed that the size of the cells increases with the increase of the total volume of the chromosomes contained in their nuclei. 3. The presence or absence of the Y-chromosome does not affect the size of the cells in spite of the considerable volume of the chromosome. 4. The loss of one fourth chromosome reduces the size of the cells considerably in spite of the smallness of the volume of this chromosome. 5. The mutant gene miniature alters the size of the cells strikingly. The epidermal cells of the wing membrane are apparent in miniature during the whole imaginal life of the fly; in wild-type and in all other mutants studied the epidermal cells degenerate soon after the emergence of the fly from the pupa. 6. The size of the cells in different races of the same species is determined by the quality as well as by the quantity of the chromosomal material contained in their nuclei.