124 W. J. MOENKHAUS 
INTRODUCTORY 
The present report includes the results of two series of experi- 
ments on the fruit fly—Drosophila ampelophila. One set con- 
cerns itself primarily with the effects of inbreeding and the other 
with sex-ratios. The experiments on inbreeding grew out of work 
I had been carrying on on hybridization. In these hybridiza- 
tion experiments the effects on the developmental processes of 
hybrids between species too remotely related were especially 
emphasized. The converse of these experiments was, naturally, to 
study the effect upon the young between individuals too closely 
related. Fishes, upon which all my experiments in hybridization 
were made, do not lend themselves for purposes of inbreeding 
without elaborate breeding facilities. Mice seemed suitable for 
this purpose but, both at the outset of these experiments and since, 
these creatures have proven miserable failures in my hands. 
Among the insects, I tried the common willow beetle but this 
proved to throw only one generation annually in this latitude. 
It was desirable to have an animal with a brief life history, whose 
food could be easily obtained at all seasons and in which the sexes 
could be readily distinguished. In these respects the fruit fly is 
almost ideal. The facts herein considered confine themselves to 
this. species. 
The experiments on sex-ratio suggested themselves in connec- 
tion with the inbreeding experiments and so were carried out 
along with the latter and after they were completed. 
MATERIAL AND METHODS 
The strain which is mostly under discussion in my inbreeding 
experiments came from a well-filled female that was taken from the 
window of my residence in Bloomington. Other strains were 
started at the onset. Some of these came from the banana bunches 
at the various groceries and others came from fruit which I had 
laid out for this purpose. None of these were carried further than 
two or three generations excepting two, called 6 and 7 in my 
records. The latter was discontinued after the tenth generation 
