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BRAIN WEIGHTS OF RATS 563 
to the expected number of one Albino to three pigmented. I 
have tried to determine whether or not the brain weight varies 
systematically with coat color. The following table gives the 
results of examination. 
CALCULATED BRAIN 
WEIGHTS INTERME-| DEVIATION FROM 
‘ a i DIATE BETWEEN CALCULATED 
LEAONDAY LIONEL JEU MUNI WSK PARENT NORWAY INTERMEDIATE 
AND PARENT VALUES 
ALBINO 
mm. gms. : per cent 
Pigmented coat. 186 1.854 1.896 —2 
Wihte.o. «.22..c¢ 195 1.860 1.947 —4 
So far as the tabular values are concerned, the hybrids with 
pigmented coats give shghtly heavier brain weights than those 
with non-pigmented coats. However owing to a somewhat 
greater mortality among the pigmented rats, it is possible that 
those which died previous to the examination might have been 
physically inferior individuals which possessed smaller brains. 
Even as it stands the difference of 2 per cent is certainly not 
high enough to be significant when the great individual varia- 
bility in the brain weights in these hybrids is taken into account. 
I am thus inclined to believe that there is no definite correlation 
between the brain weights and the characters of the coat under 
these conditions. 
REMARKS 
As has been stated, the brain weight character appears to blend 
in inheritance. In this respect the brain weight behaves like 
body size—weight and length—as well as such characters as 
ear length and skeletal dimensions in the rabbits studied by Castle 
and his collaborators (’09). 
It has been found by several investigators that in many cases 
of blended inheritance the characters under consideration show 
a greater degree of variability in the second filial generation (F.) 
than in the first filial generation (Fi). This greater variability 
in the F, has been regarded by a number of investigators (see 
