140 Francis B. Sumner 
year." The temperature conditions during the first four months 
are indicated in Fig. 1, in which a certain degree of comparison 
with those of the previous winter is made possible. The,mean 
temperature of the warm room during the first three months of 
i ee va (oF GN sive TG 
Fig. 13 Series of 1908-1909: weight at six weeks (sexes combined). 
the animals’ lives was 21.3° C., with a mean daily range of 12°|C. 
In the cold room the mean temperature during this same period 
was 3.0° C., the range of daily fluctuation being 6°. The temper- 
*' The mice here used are from an entirely new stock, none of them being descendants of those raised 
during the preceding year. Animals from several different localities, having independent pedigree, 
are comprised in the lot. In the present series individual litters were not divided into a “warm 
room” and “cold room” half, as had been done with those of the preceding year. 
~ 
