560 SHINKISHI HATAI 
weights (chart 1) we do not see any indication of discontinuity ; 
in other words the distribution of the brain wefghts is concentrated 
round the average values instead of being concentrated about 
the Norway and Albino mean values respectively. This indi- 
cates that so far as the present data are concerned the brain 
weights in the first hybrid generation are intermediate between 
those of the parents. When the continuous character of the 
distribution of the brain weights is compared with calculated 
values according to the law of probability by the formula 
y = 26.89 e — 0.1877 x2 
we note the close agreement between observation and calculation 
which justifies the statement made above. (Chart 2. F;.) 
TABLE 2 
. FI 
F, GENERATION BRAIN WEIGHT GMS. A a 
»Z] & 
oA < 
ae) Be 
Ven] © ~ fora) ° So = cS) on ~ a A isa) & 
Body length Te n 7 a 2 2 Sls = ef 3 : a 
— 4 — a — Sol nN a a a & Gal 
mm 
160-170 il 1 pF a OL 58) 
170-180 1 2 2, 5 il TO ESS 
180-190 1 1 3 1 1 2 9 | 1.81 
190-200 1 3 3 7 5 4 2 25) Wess 
200-210 1 2 3 5) if 1 19 | 1.95 
210-220 3 (oral 3 1245 2a 
220-230 4 2 5 1 12 | 2.08 
230-240 neha heal Gu2.45 
240-250 1 Tle | Past) 
250-260 1 Tes |e 1s 
Trequency 
brane weight. oe) sacri 1.6" | LOS LAC 28 |G eee 2 LO 
BRAIN WEIGHTS IN THE SECOND HYBRID GENERATION RATS (F:) 
In chart 1 the average brain weights for corresponding body 
length as well as the individual brain weights for F, are recorded. 
The averages were obtained from the correlation table (table 3). 
As is shown in the chart the average brain weights in the second 
hybrid generation are practically identical with those in the first 
