324 



Morgan. 



The origin of these two types has been already described and some 

 of the principal features in their heredity have also been recorded 

 (Science, March, 1911). In the present contribution I propose to give 

 the data on which these preliminary statements rest, also many new 

 data obtained during the present spring, for which I am mainly 

 indebted to my assistant, Mr. C. B. Bridges. With these data I can 

 now offer an explanation of certain apparently abnormal sex ratios 

 that have been observed (Proc. Sup. Exp. Biol, and Med., Feb. 1911), 



Text-Figs. 3 — 4. Fig. 3. A rare type with one normal 'long' wing and one 



miniature wing. Fig. 4. A rare type with one normal 'long' wing and one 



rudimentary-miniature wing. 



when one of these mutants (rudimentary ■wings) was crossed with 

 the other (miniature wings). I shall give also the data for the study 

 of linkage between the factors concerned in the heredity of these wing 

 characters (R and M) and the sex-linked factor for color in the eyes (C). 



It may facilitate the explanations that follow if it is recalled that 

 both miniature and rudimentary wings show sex-linked inheritance. 



If M stand for Miniature, the miniature wing wiU occur when M 

 is present, and R is absent (r), i. e, rM. If R be the symbol for Rudi- 



