74 HENRY H. DONALDSON 
as thus obtained, used as a basis for determining the relative 
weight of the brain. 
Moreover, corresponding series of animals from Philadelphia 
were to be prepared by a like technique and these data in turn 
used as standards with which to compare the European records. 
This plan was carried out, and the results furnish the material 
for the discussion which follows. 
The constitution of the several series of specimens is shown in 
tables 1 to 11 inclusive. These tables give by series the number 
of individuals and the range in body weight for each sex separately. 
TABLE 1 
Mus norvegicus from Vienna 
| NUMBER ate IN BODY WEIGHT 
| grams 
Miners 8 erent ran orb lt:. AS eats shone Mee | 38 78-400 
Ga SE PME I es pth 2, godine he ete so ogee | 55 | 68-354 
| 
TABLE 2 
Mus norvegicus albinus from Vienna 
| NUMBER |RANGE IN BODY WEIGHT 
———e += — a | —$———_$_ 
| | grams 
IMI CRtree ras 6 655. cmb eats ec ee a en 4 | 180-292 
ROTIVS Com etl as. sce tence Reale en eae 6 | 142-204 
TABLE 3 
Mus norvegicus from Paris 
S : | : as 
| NUMBER pee IN BODY WEIGHT 
| 
| grams 
EC eae se SP ahd sci aetna eee [8 EA lt 64-391 
HPemales:....2 2. MP ek 8s, a Ae es x Ae 46 | 86-389 
