FERTILITY AND STERILITY IN DROSOPHILA 171 



tion. The normal function is dominant to the negative condition. 

 An unaffected male can transmit something as a dominant char- 

 acter which causes the normal egg deposition of his daughters. 



7. The defect is sex-limited in the sense that it affects the fe- 

 male only but it is probably not sex-linked in the sense that it is 

 carried by the X-chromosome. If so, it is such a distance from 

 W that it crosses over more or less freely with it. 



I wish to express to Professor Morgan my appreciation of his 

 interest throughout the present study. I am also grateful for the 

 generous gift of the Dyckman Fund which the Department voted 

 me for 1912-1913. 



BIBLIOGRAPHY 



Castle, W. E., Carpenter, T. W., Clark, A. H., Mast, S. O. and Barrows, W.M. 

 1906 The effects of inbreeding, cross breeding and selection upon the 

 fertility and variability of Drosophila. Proc. Amer. Acad. Arts and 

 Sciences, vol. 41. 



MoENKHAUs, W. J. 1911 The effects of inbreeding and selection on the fertility, 

 vigor and sex-ratio of Drosophila ampelophila. Jour. Morph., vol. 22, 

 no. 1, pp. 123-154. 



Morgan, T. H. 1911 The origin of nine wing-mutations in Drosophila. Science 

 vol. 33. 



