INBREEDING AND SELECTION TN DROSOPHILA AMPELOPHILA 125 
since it had been from the beginning apparently less prolific. 
The strain 6 was carried for over seventy-five generations and is 
the one on which the experiments in inbreeding of this report are 
based. 
For vivaria, tall stender dishes, tumblers, quinine bottles and 
lamp chimneys were given a trial. They were discarded in favor 
of 8-dram shell vials. These were compact, so that a large number 
of matings could be kept in a small space, and they were most con- 
venient in manipulating the pairs during the frequent changes to 
new cages that was necessary all along. The open end of the 
shell vial was closed with a plug of absorbent cotton, not too 
compact, so as to afford some ventilation. The flies are strongly 
positive to light, so that the vials could be laid with their bottom 
toward the light and the cotton plug removed with safety for the 
introduction of food etc. Small trays holding fifteen of these 
vials were used and in this way the experiments could be readily 
and compactly stored in the incubator, or they could be packed 
into a valise to be taken along wherever I went. The food was 
exclusively well-ripened bananas. To prevent the larvae ‘rom 
pupating in the food, narrow strips of blotter or filter paper were 
introduced in which they seemed to be especially fond of pupating. 
It is, of course, apparent that the greatest care had to be taken 
to avoid contamination from flies without. The stock food had 
to be scrupulously watched and the instruments kept clean to 
avoid the introduction of eggs laid on them by extraneous females. 
The bananas, especially, as they come from the stores, are likely 
to be infected with eggs and larvae if the skin be in any way bruised 
or split. 
The brothers and sisters were paired off, always within the 
first ten or twelve hours of their life as imagos. Up to this time 
mating has not occurred. In fact I have never found a pair that 
copulated during the first twenty-four hours or, if so, that pro- 
duced fertile eggs. 
