Abstract
1. The eye color pigments may be classified into reddish and yellowish. As to their distribution in an ommatidium, primary, secondary and basal pigments can be distinguished.
2. Various mutations in eye-color result from modifications either in distribution, quality, quantity or in the rate of development of the pigments. The mutant genes act always as inhibitors (except in the case of the change in quality).
3. Five sets of‘parallel’mutations in eye-color found between D. melanogaster and D. virilis were tested from the above view-points. Of these three have been proved to be really‘parallel’in the mode of development of pigments, but two belong to quetionable cases.
4. In respect to quantity, distribution, or in the time of the first appearance of the pigments, the individuals which are homozygous for two eye-color mutant genes, show only the part which is free from the action of either gene.
In consequence of combination of two genes, a“white eye”is sometimes produced. This is mainly due to the cumulative action of the combined time modifications of the two genes.
5. In respect to the quality of reddish pigments, heterostatic relations may be received.
