INHERITANCE OF ABNORMAL VENATION. 11 
HISTORY OF THE PEDIGREED STRAIN. 
Before taking up the data concerning inheritance, it will be well to out- 
line briefly the history of the chief pedigreed strains. Further details 
are given in table 36. Mating 211 was the first family in these lines of 
which a large number of offspring were described. Both parents were 
abnormalin both wings. The wings of 177 offspring of this mating were 
sketched. It was found that 31 per cent of the males were abnormal 
and 65 per cent of the females. Successive generations after this, 
breeding brother with sister, gave the following results: Abnormal 
female by normal male (mating 257), 70 per cent of each sex abnor- 
mal; abnormal female by abnormal male (mating 284), 62 per cent of 
the males and 96 per cent of the females abnormal; abnormal female 
by normal male (mating 330), 96 per cent of the males and 91 per 
cent of the females abnormal; abnormal female by normal male (mat- 
ing 367), 64 per cent of the males and 91 per cent of the females abnor- 
mal. A number of matings were made from the offspring of No. 367. 
Matings 405 and 408 are of especial interest. 
In both of these matings both parents were abnormal in both wings. 
Unfortunately there were a small number of offspring from each (25 
and 29, respectively); but all of the offspring of mating 405 were normal 
and all those of mating 408 were abnormal. Three matings were made 
from the offspring of 405. Of the 385 offspring of these, not a single 
one showed the slightest trace of an abnormality, while of the 51 
offspring of mating 440 (the parents being children of 408) only one, a 
male, was free from abnormal venation. Mating 405, then, became the 
starting-point of the ‘‘normal strain’’ and mating 408 the starting-point 
of the ‘‘abnormal strain.”’ 
As can be seen from table 36, the various generations of the abnormal 
strain gave approximately, sometimes actually, 100 per cent abnormal 
flies, although normal individuals were far from rare. Furthermore, 
the intensity of the abnormalities increased. The greatest abnormality 
noticed before the fifth generation is shown in fig. 20. Up to that time 
all abnormalities were confined to the second longitudinal vein. Begin- 
ning with the sixth generation, abnormalities appeared on the third 
longitudinal vein. They became frequent by the tenth generation. In 
the fifteenth generation they were common and abnormalities began to 
be noticed on the fourth longitudinal vein. These have, even yet, rarely 
exceeded small spurs near the distal end. About this time the fifth 
longitudinal vein also began to be affected, and specimens such as are 
illustrated in figs. 30 and 82 were found. Meanwhile increasingly great 
abnormalities on the second and third longitudinal veins occurred. (See 
figs. 37 to 42 for examples. The condition shown in fig. 43 is unique. ) 
Turning now tothe normal strain, three points should be borne in mind: 
the parents in each generation were normal, it came from the same 
