;98 
IOWA ACADEMY OF SCIENCE 
12 
lb. 
granddams — mean 
production 
of 
granddaughters 
17.41 
lbs. 
13 
lb. 
granddams — mean 
production 
of 
granddaughters 
16.89 
lbs. 
14 lb. 
gr andd ams — mean 
production 
of 
granddaughters 
17.68 
lbs. 
15 
lb. 
granddams — mean 
production 
of 
granddaughters 
17.5 
lbs. 
16 
lb. 
granddamsi — mean 
production 
of 
granddaughters 
17.66 
lbs. 
17 
lb. 
granddam s — m e an 
production 
of 
granddaughters 
17.2 
lbs. 
18 
lb. 
granddams — mean 
production 
of 
granddaughters 
18.48 
lbs. 
19 
lb. 
granddams — mean 
production 
of 
granddaughters 
17.69 
lbs. 
20 lb. 
granddam s — mean 
production 
of 
granddaughters 
16.32 
lbs. 
21 
lb. 
granddams — mean 
production 
of 
granddaughters 
15.5 
lbs. 
22 
lb. 
granddams — mean 
production 
of 
granddaughters 
25.0 
lbs. 
23 
lb. 
granddams — mean 
production 
of 
gran d daughters 
20.44 
lbs. 
24 
lb. 
granddams — mean 
production 
of 
granddaughters 
20.66 
lbs. 
25 
lb. 
granddams — mean 
production 
of 
granddaughters 
23.0 
lbs. 
26 
lb. 
granddams — mean 
production 
of 
granddaughters 
23.5 
lbs. 
27 
lb. 
granddams — mean 
production 
of 
granddaughters 
20.0 
lbs. 
28 
lb. 
granddams — m e an 
production 
of 
granddaughters 
20.33 
lbs. 
A tabulation of the variates within these limits reveals the fact that 
the granddams having records above 21 lbs. produced F 2 descendants, as 
follows : 54 above 21 lbs. and 60 below. The granddams below 21 lbs. 
produced 764 below 21 lbs. and 104 above. The latter appears to be a 
7 :1 ratio, indicating a linkage of two factors, — one a pure dominant, the 
other probably sex-linked acting in a simple 3 :1 ratio. 
These facts, it is true, go but a very short way in the solution of this 
problem, but it is hoped that they may afford an indication of the means 
for further investigations. 
In the work just reviewed, the points to be noted are : 
1st. The relation between the percentage fat composition of milk, and 
the proportion of fat globules of different sizes. 
2d. The prepotency of dams in transmission of fat production to their 
offspring as evidenced by the correlation coefficient .29 indicating sex- 
linkage of some of the factors of fat inheritance, and, 
3d. The segregation of fat factors in a 7:1 ratio showing further evi- 
dence of linkage of factors in the inheritance of fat content of milk. 
