4 EXPERIMENTS WITH DROSOPHILA AMPELOPHILA. 
DESCRIPTION OF ABNORMAL VENATION. 
It is probable that all insects occasionally show some abnormality of 
wing-venation. In my experience with Drosophila ampelophila they 
occur in one-third of 1 per cent of wild specimens. The data concern- 
ing this point are given in table 1. In these the abnormalities consisted 
of irregularities of the second longitudinal vein or small dashes near its 
distal end (similar to figs. 8 to 10). Only one of the 19 abnormal* wild 
flies I have seen was abnormal in both wings. 
TABLE 1.—Percentage of wild Drosophila ampelophila 
which have extra veins in their wings. 
| Percent- 
Abnor- 
eens | mal. banca 
2 | | 
Bloomsburg, Pa. ...... | 1165 8 0.68 
Huntington, N. Y. ... GOT) 3 0.43 
Woods Hole, Mass.... 2088 3 Ona 
Boston, Mass........... | 1660 5 0.30 
et 2 a 8 5605 | 19 | 0.34 
While rearing this insect for another purpose, several such abnormal 
specimens were found in one family. My principal abnormal strain, in 
which the variety and amount of abnormality is little short of astound- 
ing, came from these. The various figures give a better conception of 
what was obtained than would verbal description. There is the utmost 
variation in the abnormal venation, not only in different flies, but in the 
different wings of the same fly. The majority of the abnormalities are 
in the distal portion of the marginal cell, but they have been found also 
in the submarginal and a few in the first, second, and third posterior 
cells, affecting all the longitudinal veins except the first. 
CORRELATION BETWEEN THE RIGHT AND THE LEFT WINGS. 
One wing may be abnormal, or both may be. In the latter case the 
abnormality may be great in one wing, small in the other; on one vein 
in one wing and lacking on this vein but present on others in the other 
wing (see figs. 44 to 46). Nevertheless there is a correlation between 
the intensity of the abnormality in the two wings, as is made clear by 
tables 2 and 3. In drawing up these tables the range of variation of 
the intensity of the abnormality was divided arbitrarily, since the char- 
acter is not quantitatively measurable, into six classes: normal vena- 
tion (or zero intensity of the abnormality), very slight (see figs. 3 to 7), 
slight (see figs. 8 to 11), medium (see figs. 12 to 18), great (see figs. 
19 to 24), and very great (see figs. 25 to 35). To which class a given 
wing should be assigned is a matter of judgment; but since when these 
tables were made up it was thought that there was no correlation be- 
*Unless otherwise stated ‘‘abnormal venation’’ means, throughout this paper, 
‘‘veins added.”’ 
