Oswald H. Latter 
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doubt. Unfortunately I had not material sufficient to determine trustworthy means 
of length and breadth of Wren's eggs, but I have estimated them from measure- 
ments given in inches by W. J. Gordon in Oui' Country s Birds, and feel confident 
that no error of any importance exists in his figures, for the measurements given 
by him of other species' eggs approximate very closely with the means obtained 
by myself in each case. It will be seen that the egg of the Wren is far smaller 
than that of any other species with which we are dealing, and that the lengths 
and breadths of Wren-Cuckoos' eggs are very much less than those of other 
Cuckoos. For the other species where the differences are significant this sense 
of the variation is not clear so far as it concerns breadth, though it appears to 
be so in the matter of length : the two subjoined tables give the comparison. 
Meiin Length 
Hedge-Sparrow-Cuckoo 2.3'1 
Tree- Pipit-Cuckoo ... 2.3-1 
Meadow-Pipit-Cuckoo 22-3 
Wren-Cuckoo 21-1 
Hedge-Sparrow ... 20'1 
Tree- Pipit 20-0 
Meadow-Pipit 19-7 
Wren 17-7 
Mean Breadth 
Hedge-Sparrow-Cuckoo 16'8 
Meadow-Pipit-Cuckoo 16-7 
Tree-Pipit-Cuckoo ... 16-6 
Wren-Cuckoo 15-8 
Tree-Pipit 15-1 
Hedge-Sparrow ... 14'7 
Meadow-Pipit 14-6 
Wren 12-7 
Colour-matching . 
As already stated, 288 Cuckoo's eggs were examined in this connection and 
compared with the eggs among which they had been deposited. In 39 cases 
the matching was extremely close, and in a further 109 there was a fair 
approximation, rendering the Cuckoo's egg more or less similar in appearance 
to those of the foster-parent, the two categories giving a total of 148 eggs 
more or less closely matched to their several clutches, or at any rate within the 
limits of colour-variations exhibited by the species in question. Reh has observed 
this last same phenomenon in nests of the Red-backed Shrike (Lanius collaris), 
and eggs of this description possess an especial interest, for they seem to afford 
very strong support to Prof. Newton's theory. It is a fairly frequent occurrence 
to find in the nests of birds whose eggs exhibit considerable variation of colour, 
e.g. Meadow-Pipit, Tree-Pipit and Reed- Warbler, a Cuckoo's egg, not resembling 
the particular clutch in which it occurs but which would match eggs of another 
clutch of the same species. On the other hand, I found but three instances of 
Cuckoo's eggs with a close resemblance to eggs of any one species being deposited 
elsewhere than in the nests of that species, viz. egg No. 152 found in nest of 
Lesser Whitethroat is a good match to a Meadow-Pipit's eggs; No. 173 in nest 
Biometrika i 14 
