176 The Cuckoo's Egg 
Length of Cuckoo's Egg. 
K 

— 
8 
1 
i3 SO ex c 'a at ea e« 
Length of Cuckoo's Egg in mm. 
The curves give fairly reasonable graduated values, considering : (i) the paucity 
of data, and (ii) the possibility of class differences within the race indicated in 
this memoir. 
APPENDIX IV. 
Table of Egg Measurements. 
The following is a summary of my measurements on the Cuckoo's and other 
birds' eggs. I have added the results of recent measurements on the eggs of 
House-Sparrow, Blackbird, Song-Thrush, Starling and Linnet made by Professor 
Pearson and some of his co-workers. The whole serves to illustrate the relative 
smallness of the Cuckoo's egg. 
Bird 
Approxi- 
mate length 
in inches 
No. of 
Cases 
Length of 
Egg 
Breadth of 
Egg 
Mean 
S. D. 
C. of V. 
Mean 
S. D. 
C. of V. 
Cuckoo 
14 
24.3 
22-40 
1-0585 
4-72 
16-54 
-6496 
3-93 
Blackbird 
10 
114 
29-44 
1-3568 
4-61 
21-73 
•7874 
3-62 
Song-Thrush ... 
9 
151 
27-44 
-9988 
3-64 
20-69 
•5162 
2-50 
Starling 
8—8-5 
27 
29-78 
1 0973 
3-68 
21-76 
-4233 
1-94 
Wagtail* 
7—8 
16 
20-75 
1-4448 
6-96 
14-67 
•3703 
2-52 
Yellow- Ammer 
7 
32 
21-55 
•6821 
3-17 
16-04 
-4045 
2-53 
Tree-Pipit ... 
6-5 
27 
20-01 
-6978 
3-49 
15-09 
•4488 
2-97 
Meadow- Pipit 
6 
74 
19-72 
1-2504 
6-37 
14-56 
-5611 
3-84 
House-Sparrow 
6 
687 
21-82 
1-1946 
5-47 
15-51 
-5245 
3-38 
Hedge-Sj)arrow 
6 
26 
20-12 
-8096 
4-02 
14-73 
-4146 
2-81 
Robin ... 
6 
57 
20-22 
-8565 
4-24 
15-43 
•4771 
3-09 
Linnet... 
5-5—6 
65 
17-14 
•5984 
3-49 
13-33 
•3581 
2-69 
* This was a mixed series made up of 6 eggs of White-Wagtail, 7 of Pied-Wagtail and 3 of Blue- 
headed- Yellow-Wagtail. This accounts for the great variability in length. We see that the Cuckoo's 
egg is the most variable of the whole series in breadth and with the exception of the Meadow- 
Pipit's and House-Sparrow's the most variable also in length. The biggest of all the birds here 
dealt with, the Cuckoo has an egg hardly longer than the House-Sparrow's or broader than the Yellow- 
Ammer's. 
