ance with its local surroundings and can have no fixed scale of variation, 
the egg, equally with the bird, must have a fixed and uniform scale of 
variation in accordance with the latitude or altitude at which it is found, 
most particularly in size and measurements. 
1'he following table of accurately measured specimens actually collected 
in the sections named, gives what I believe to be fairly accurate av¬ 
erages, and a surprisingly uniform scale of gradation in size from South 
to North and from East to West in the Humid Province. Owing to the 
small amount of data at hand, 1 am unable to trace an unbroken line of 
variation in the Arid Province ; but from that at my disposal I find 
the minimum to be on the coast of California, and the maximum in the 
south-western portion of Washington, with Colorado between. This 
increase or decrease in measurements in different localities needs no other 
explanation than that which has already been given as the probable cause 
of the increase or decrease of the number of eggs in a set ; which is 
too well known to all ornithologists to warrant further comment 
M EASUREMENTS. 
LOCALITY. 
MEASURED. 
\l 
A XI 
M 
r 
M. 
MINIM 
V 
M. 
AVR 
RAG 
rK. 
North Carolina. 
27 
I 
•73 
X 
1 
.26 
1 
•48 
X 
1 
,08 
1.02 
X 
I 
• 14 
Pennsylvania. 
225 
2 
. 06 
X 
1. 
. 12 
I 
42 
X 
I, 
°5 
1.64 
X 
I. 
15 
New York. 
320 
2 
03 
X 
1. 
33 
l 
43 
X 
I 
.08 
I .65 
X 
1. 
15 
New England. 
97 
I 
86 
X 
1. 
40 
I. 
43 
X 
I. 
. 12 
1.66 
X 
I. 
1 7 
t) , lnd.. S. Mich.... 
4-4 
I 
79 
X 
1. 
19 
1, 
55 
X 
I, 
. 10 
1 .(>8 
X 
I. 
1 7 
Ill., S Wis . la. 
I 32 
I . 
95 
X 
1. 
27 
1 . 
5 1 
X 
1 . 
13 
1.68 
X 
I . 
18 
Minn., N L)a . Mana. 
35 
I . 
94 
X 
1 
40 
I 
55 
X 
1 
•17 
1-73 
X 
I . 
27 
California . 
29 
I 
•78 
X 
1 
. 16 
1 
•4« 
X 
] 
03 
1.61 
X 
I . 
13 
Colorado ... 
17 
I 
.72 
X 
1 
14 
I 
59 
X 
I 
13 
1 63 
X 
1 . 
15 
Washington . 
M 
I 
.S3 
X 
1 
19 
I 
.64 
X 
1 
. r 2 
1.71 
X 
1 . 
18 
I also have measurements from Ontario, Maryland, Tennessee, Mis¬ 
souri, Kansas, and Nebraska, but so few in number that the averages 
could not be that of the localities named, and therefore can have no 
bearing on the subject. It is safe to make the assertion that there is an 
increase of about one-hundredth of an inch in the' measurements of the 
average egg, corresponding to an increase of about two and one-half de¬ 
grees in latitude or its equivolent in altitude. The increase from East to 
West is not so pronounced nor constant, yet the data at hand shows an 
average increase of one-hundredth of an inch to a corresponding increase 
of four degrees of longitude from the Atlantic seaboard to the western 
limits of the Humid Province. The surprisingly great difference be¬ 
tween the maximum and minimum eggs (.64x 35) leads one to speculate 
on the probable number of eggs of Cori'us Itmericanus to be found in 
certain of the innumerable oological collections, masquerading under the 
