THE EGG OF CUCULUS CANORUS. 
AN ATTEMPT TO ASCERTAIN FROM THE DIMENSIONS OF THE 
CUCKOO'S EGG IF THE SPECIES IS TENDING TO BREAK UP 
INTO SUB-SPECIES, EACH EXHIBITING A PREFERENCE FOR 
SOME ONE FOSTER-PARENT. 
SECOND MEMOIR. 
By OSWALD H. LATTER. 
(1) On the Existence of Cuckoo Gentes. 
In my previous paper {Biometrika, Vol. I. No. 2, January 1902, pp. 164 — 176) 
I examined this and certain other questions relating to the egg of the Cuckoo. On 
that occasion I had measurements of only 243 eggs. I have now been able to 
obtain the dimensions of 1572 specimens (including those dealt with previously) 
and am therefore in a position to speak with more confidence. Of this number, 
717 eggs were measured by myself; and I must here take the opportunity of 
recording my grateful thanks to Prof A. Newton of Cambridge, Dr E. Hartert of 
the Tring Museum, Mr F. Norgate of Bury S. Edmunds, Mr J. H. Gurney of 
Keswick Hall, Norwicli, and many other private collectors for their couitesy in 
granting me help and access to their collections. I am further indebted to a large 
number of my pupils at Charterhouse for assistance in tabulating the measure- 
ments and in checking the accuracy of the calculations. The remaining 855 
specimens were measured by Eugene Rey of Leipzig, and the dimensions published 
in Zoologische Vortrdge herausgegeben von W. Marshall, Leipzig, 11th Heft, 1892; 
Ornithologische Monatschrift d. Deutschen Vereins z. Schutze dev Vogelwelt, xix. 
Jahrgang, 1894, No. 5; and Journal filr Ornithologie, XLiii. Jan. 1895. 
In the present instance I have confined myself to the attempt to ascertain if 
the eggs of Cuckoos deposited in the nests of any one species stand out as a set 
apart from Cuckoo's eggs deposited elsewhere. The series includes eggs taken 
from the nests of no less than eighty-four different species of foster-parents, in 
addition to a number whose history was not ascertainable. From the nests of six- 
teen species of foster-parents sufficient Cuckoo's eggs were obtained to make it 
