INHERITANCE OF ABNORMAL VENATION. 3 
upon moist blotting-paper in a small vial, from which the adults could 
readily be transferred to an etherizing vial as they emerged. 
When mating was to be done the sexes were always separated before 
they were a day old. Usually no female was used as a parent that was 
more than 12 hours old before being isolated from the males. Numer- 
ous tests showed that no females so treated laid fertile eggs. Only 
rarely was there a difference of more than one day in the ages of the 
parents, and they were usually mated before they were two days old. 
For practical reasons, parents were killed after 50 to 100 offspring had 
been secured. It was found that neither the percentage of abnormal 
offspring nor the intensity of their abnormalities changed with the age 
of their parents, so that this procedure was permissible. 
In this paper only those families are considered which are in or close 
to the main line of descent. I have not thought it worth while to include 
any families having less than 40 offspring unless they were in this main 
line. Typical data are given in table 36, page 31. I have tried to arrange 
these so that they will be available for further work by those interested. 
They should not, however, be used for more than they are worth. For 
example, one can not study the inheritance of fecundity from them, as in 
but few cases have I bred from a female until she died a natural death. 
All individuals, both parents and offspring, have been kept for refer- 
ence and are deposited in the American Museum of Natural History. 
When of especial interest, the wings were mounted on glass slides in a 
thin layer of paraffin. This was found to be an excellent method of 
preservation. By all other methods which were tried the veins were 
rendered more or less transparent. When, as in making matings, it 
was desired to examine live flies, they were slightly etherized. They 
completely revive in a few minutes. All examinations for abnormalities 
in wing-venation must be made witha lens. 
Occasionally the larve were attacked by a disease (?) of unknown 
origin which caused them to crawl out of the food, elongate, and die. 
When this disorder appeared in a dish it was usually fatal to all the larvee 
in that dish. Otherwise, Drosophila bears confinement very well. Prac- 
tically all the larvee which hatch complete their development. My ex- 
perience confirms the results reached by Castle (1906b) that the closest 
inbreeding may be practiced with this fly for generations with no injuri- 
ous results. Such inbreeding was the rule in this work, being necessary 
in long-continued breeding unless unpedigreed stock be used. 
DESCRIPTION OF NORMAL VENATION. 
The normal venation of Drosophila is extremely simple, as is shown 
by fig. 2. The costal vein reaches to the fourth of the five longitudinal 
veins. The auxiliary vein is incomplete or indistinct. The anal cell is 
present. The discal and second basal cells are united and the first pos- 
terior cell is not appreciably narrowed in the margin. 
