Abstract
The character“bent” in D. melanogaster is a member of the“fourth linkage group”in that species. 1 The genes for this and the other two characters now known in this linkage group have been shown by Bridges 2 to be“carried”by the small, dot-like“fourth chromosome.”Bent is characterized mainly by two variable modifications, one affecting the wings, the other the legs. The wings vary from“normal”through a series of modified shapes including spread wings, narrow wings, broad wings, swollen wings and most frequently wings that are bent sharply backward at a point near the base. The legs likewise vary from a“normal”condition through a series of stages in which progressive degrees of shortening and twisting is exhibited, beginning with the basal tarsal joint of the hind legs. The extent of the modification seems to be influenced considerably by environmental conditions.
Some time ago I found in Drosophila virilis a mutant character which bears considerable resemblance to this bent in D. melanogaster both in appearance and behavior. It exhibits much the same series of variable leg and wing modifications, except that those of the wings are less extreme and less frequent—the sharp bend being absent entirely. There are several lines of evidence pointing toward the conclusion that these characters in the two species are homologous, and that the gene for bent is in the small, dot-like chromosome in virilis as it is in melanogaster. Most of this evidence will be considered elsewhere, however. The present paper deals primarily with the effects of temperature on the two characters.
Since the characters show indications of homology and are both influenced by environmental conditions it is of interest to ascertain whether or not they react similarly to similar conditions.
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