54 
KNOWLEDGE. 
February, 1914. 
commonest, bv a long way, with one hundred and 
five eggs. They come in the following order : 
Type. 
Number of Eggs. 
C 
E 
B 
A 
F 
H 
D 
T 
G 
105 
60 
49 
27 
24 
13 
8 
7 
4 
Types with a distinct circle on the round end 
were A, E, F, and I. They total one hundred and 
eighteen. This represents nearly thirty-nine per 
cent, of the total, and the rings are therefore in the 
minority. One egg was found with the ring half¬ 
way down, while two more were found with heavy 
markings on the pointed end, while the round end 
was almost free. 
Clutches of two eggs each, in which both eggs 
belonged to the same type of mottling, were in the 
minority. Out of sixty-six clutches with two eggs 
each twenty-eight had both eggs belonging to the 
same type. In the remaining thirty-eight it is 
remarkable how frequently the types E and C and 
A and C occur together. The only difference 
between A and E is that the one has more markings 
on the lower part of the egg than the other ; and, 
if they be considered as one type only, the frequency 
of occurrence is even more marked. In clutches 
of three the percentage of this combination is even 
higher. Out of thirteen of these clutches only one 
had all three eggs belonging to the same type of 
mottling. In type B (see Figure 50) the twist on 
the markings should be brought to notice. Where it 
existed this twist was always in the same direction, 
downwards from the right to the left. The same 
thing occurs in the eggs of the Lesser Tern, and is 
undoubtedly connected with the laying apparatus 
of the parent bird. 
In recording the ground colour a graduated scale 
was used, a-k. The eggs were marked according 
to their shade. On the photograph ot the scale 
(reproduced in Figure 50) the true colour values 
have unfortunately not come out, and the scale is 
consequently misleading. On the original the 
gradation is quite regular. 
In clutches of two eggs each the minority had 
both eggs of the same ground colour. In some 
cases the difference was enormous. One clutch 
contained eggs of types a and h respectively. 
Others varied to the extent of c and g, e and i, 
c and /, b and /. Only a single egg was found to 
match type k. 
There were three eggs that could not be accom¬ 
modated to this scale. One was of a dull slate 
colour, with mottling also outside the scale. It was 
with a normal egg. The other two made one clutch. 
Both were as blue as a thrush’s egg. Mottling was 
also abnormal on both. It is a curious coincidence 
that both ground colour and mottling should be 
abnormal on all three eggs. 
In clutches of three eggs three clutches had all the 
eggs of a different ground colour. One clutch had 
all three eggs alike. Of the other nine, all had two 
eggs alike; with two exceptions only, these were 
lighter than the third. 
In length the eggs varied from 3-6 centimetres 
to 4-7 centimetres; in breadth, from 2-6 centi¬ 
metres to 3-7 centimetres. The smallest egg was 
the same length, but a little broader than a normal 
egg of the Lesser Tern (see Figure 50). F on the same 
figure shows the broadest egg found. It was as 
broad as the above was long, and not much 
longer than its own breadth. 
No direct connection could be found between 
types of eggs and types of nest. There may be 
none. But a point suggested by our work is 
that a bird laying one type of egg may lay another, 
type also, but not any type. There may be a law 
controlling range of variation possible to one bird. 
It remains to be proved that, where extreme differ¬ 
ences were found, these were produced by the same 
bird. We found that, where a dark and light egg 
existed together, the lighter was usually the more 
heavily marked. 
The use of material for nesting, alike in quality 
and quantity, is probably more according to law 
than is usually believed. 
Other laws suggest themselves, but they cannot 
be proved till more work has been done on 
these tedious and somewhat novel lines. Many 
interesting results should be attainable. 
Reprinted from Knowlkdgi: {with which is incorporated Hardwicke's Science Gossip, 
and Illustrated Scientific News). Volume XXXVII. Number 547 ( February, 1914). 
Pages 52-54. 
