Egg Coloration in the Cuckoo, Cuciulus canorus. 105 
The following are possible explanations :— 
(a) The resemblance between the eggs of each of the “sets” is 
coincidence merely, the eggs of a “set” being the product of two or 
more birds. 
(0) The eggs of each set are the product, of a single bird. 
Now, should the former view be accepted and the theory of Cuckoo 
“gentes” be also adhered to, we have the following facts to face. We must 
hold, generally, that in each of the supposed “sets” there are as. many 
Cuckoos represented as there are foster species. We need not postulate more, 
although there might be more. 
For example: - 
Set I. Two eggs : One foster species. 
Set II. Four eges d ¥ : Two as 
Set III. Two eggs : Two 5 
Set IV. Two eggs : ; ; Two 2 
Set V. Three eggs. j : Three is 
Set VI. Six eggs 5 3 ; Five 3 
Set VII. Eleveneggs . : ; Four 
Set VIII. Threeeggs  . : : Three 3 
Set IX. Threeeggs . : Three i; 
Set X. Seven eges. s Four i 
Set XI. Two eggs : Two 53 
Set XII. Threeeges . : Three : 
Set XIII. Two eggs : : é Two 3h 
- What is the probability, we may pertinently ask, of five distinct birds 
(Set VI.) in the same district all laying in the same season, each in a separate 
Joster-species nest, eggs so resembling each other in ground hue, depth and 
distribution of superimposed pigment that they cannot be distinguished 
from each other? Such is not likely to be the case; the probability is very 
remote. 
_ A similar argument applies to the other sets. Take Set VII. Here also 
it is highly improbable that four birds will, amongst them, lay ten eggs 
which in colour cannot be distinguished from each other. And so with the 
other groups. : . 
Let us consider the other alternative. The eggs of the groups or 
“sets” discussed in this paper may be regarded as the product of a 
single bird. To most observers who may examine these eggs, this will 
probably be the more acceptable alternative. It involves fewer difficulties. 
