76 HENRY H. DONALDSON 
TABLE 9 
Mus norvegicus from Philadelphia 
NUMBER RANGE IN BODY WEIGHT 
7 : : grams 
Males ch) Se occ Ae oe eee | 49 104-533 
Menmialess si «2a ye soe ee rh 46 75-457 
TABLE 10 
Mus norvegicus albinus from Philadelphia. Prepared in 1910-11 
NUMBER RANGE IN BODY WEIGHT 
F : grams 
Ma eS ee A. aes See en ats or ea mee eee 9 101-194 
Hemaless 4.335 errr eae ee dee 11 72-124 
TABLE 11 
Mus norvegicus albinus from Philadelphia and Chicago. Material prepared in 
1907 by Dr. Hatai 
NUMBER RANGE IN BODY WEIGHT 
| grams 
Ninleceeee es Nee | bet a ee eae | 41 | 112-292 
Females tee es a a eee Ce | 35 108-253 
An examination of the data for the four longer series—namely 
those for the wild Norways—used in the determination of cranial 
capacity (tables 1, 3, 6 and 9) suggests several comments. In 
collecting these series no selection by either size or sex was made 
by me, and yet the proportion of the sexes is rather similar in all 
four. In the three European series, the range in body weight is 
also similar, while distinctly heavier rats are found in the Phila- 
delphia series. It may be remarked that in this latter case we 
received every animal caught, while it is just possible that in the 
case of some of the European series, the dealers reserved the 
very largest animals for their own use, and in this way modified 
the range in body weight. However that may be, the data as 
they stand show that the several series were taken from rat popu- 
lations which were similar in their general composition. 
