166 
Journal of Agricultural Research 
Vol. XXVI, No. 4 
produced 17 of the monsters among 79 young, 4 * * or 21.5 per cent. A third 
fairly noteworthy cluster takes its origin in mating 13-16-3 from which 
nearly 3 per cent have been otocephali. This line has a common ancestor 
with 13-13-1 only in the ninth generation. (Table II.) 
Table II .—Number and percentage of otocephali among the descendants of particular 
matings in Family 13. The mating is designated by the generation followed by an 
arbitrary number 
Matings of Family 13. 
Descendants. 
Otoce¬ 
phali. 
Total 
young. 
Per 
cent 
otoce¬ 
phali. 
O—I. 
O 
404 
O 
0-2. 
5 ° 
2,849 
1.8 
2-6,7. 
0 
201 
O 
2-5 . 
50 
2,636 
i -9 
3~*3 . 
O 
301 
0 
3 ” 11 . 
2 
150 
i -3 
3 ~ 12 . 
47 
2, l68 
2. 2 
4-9 . 
0 
I96 
0 
4-18. 
47 
1,960 
2.4 
8-11. 
5 
625 
0.8 
8-3. 
42 
1,291 
3-3 
I 3“7 . 
13 
637 
2. 0 
16-3. 
7 
263 
2. 7 
13-1. 
26 
29I 
8.9 
19-1. 
17 
79 
21. 5 
Excluding mating 19-1 
and descendants. 
Otoce¬ 
phali. 
Total 
young. 
Per 
cent 
otoce¬ 
phali. 
Otoce¬ 
phali. 
Total 
young. 
Per 
cent 
otoce¬ 
phali. 
33 
2, 770 
I. 2 
24 
2.558 
0.9 
33 
2,557 
1-3 
24 
2,345 
I. 0 
30 
2, 089 
1.4 
21 
1,877 
1. I 
30 
1, 881 
1. 6 
21 
I, 669 
*•3 
25 
1, 212 
2. I 
l6 
I, OOO 
1.6 
9 
212 
4. 2 
Excluding mating 13-1 
and descendants. 
Summing up, we may say that of six early sublines of Family 13, four 
showed no tendency to produce otocephali, while the other two probably 
soon acquired, if they did not start with, a tendency to produce about 
1 per cent. One of these became the main line of the family and gave 
rise to several important branches, all of which showed the tendency to 
an unusual extent. A sudden jump to about 4 per cent seems to have 
occurred at some point in one subline, with a second jump in the same 
line, six generations later, to more than 20 per cent. 
The distribution within Family 13 adds to the evidence for heredity 
as an important basic factor. The mechanism of this heredity, however, 
is far from clear. 
A single recessive factor is as much out of the question as a dominant 
factor. The ratio of normals to otocephali is 493 to 50 (9.9 to 1) in 
Family 13, and 346 to 32 (10.8 to 1) in other families within those matings 
which produced at least one of the monsters. It can not be doubted 
that a great many other matings have an equally strong tendency. In 
fact, 43 of the 58 matings included above produced only one otocephalus 
each, 11 produced only two each, leaving only 4 which have produced 
three or more. If each mating had produced several hundred young 
instead of about 16 on the average, there can be no doubt that the ratio 
would be nearer to 100 to 1 than 10 to 1, except in the small cluster 
of matings descended from 13-19-1. 
4 Ten more otocephali and 36 normal young have been produced by this line since this tabulation, i. e., 
from July, 19*3, through September, 1923, making a total of 27 otocephali out of 125 young, or 31.6 per 
cent. 
