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 with a lens. 



Occasionally the larvae 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 larvae 

 in that dish. Otherwise, Drosophila bears confinement very well. Prac- 

 tically all the larvae which hatch complete their development. My ex- 

 perience confirms the results reached by Castle (19066) 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. 



