THE J. H. OWEN COLLECTION OF BRITISH BIRDS' EGGS. 275
but more particularly in the colour and type of its markings.
It is this tendency to variation which renders series of sets of
eggs, such as we are now considering, so useful to the student.
There is, of course, great variation of all kinds between different
species ; we may compare sets of twelve tiny spotted eggs of
the Blue and Great Titmice with the large single and heavily
decorated egg of the Guillemot. There is also a great range
of variation in the eggs of the same species and, in lesser
degree, in the eggs of the same individual. In fact one might
go so far as to say that no two eggs, apart from those which are
monochromatic, such as are laid by many hole-nesters, are
exactly alike. These differences are demonstrated throughout the
collection but we may draw attention to some which are specially
suitable as illustrations. Differences of texture are probably
the most difficult to deal with, but a comparison of the highly
polished eggs of the Kingfisher with the chalky eggs of the
Little Grebe show that between certain types of birds the degree
of divergence is very pronounced. In the drawer, fifth up,
single mahogany cabinet, is a series of the eggs of the Carrion-
Crow, which exhibit a great variation in shape and size, some
being elegantly elongated. In large cabinet, drawer 1, we see
a fine series of Chaffinchs' eggs, which illustrate variation of
size in another type of bird, and in the next drawer, 2, is an
unusually large set of Bullfinch's eggs, marked Saling, 31.5.13.
There are remarkable examples of midget eggs, which include
a set of 5 Rook's eggs, Barnston, 19.3.33, which are about
half the usual size and stated to have been yolkless, two Sky-
lark's eggs not one third of normal size ex set of 4, Little Dun-
mow, 27.5.21, an egg of the Lapwing less than half normal
size, dated 3.4.36, and two Song Thrush's eggs less than half
of the usual dimensions. Unusually large sets are well represented
and as examples we may mention the following: Rook, a set
of 7 ; Linnet, a set of 7 ; Red-backed Shrike, a set of 7 ; Song-
Thrush, a set of 6 ; and Lapwing, 3 sets of 5. Pronounced
variation of colour and markings is, in some species, more the
rule than the exception and some species thus affected lay
regularly different types of eggs, which are well known to, and
recognised by, oologists. Few species illustrate the different
phases of variation better than the Tree-Pipit and the extent
and nature of this may be seen in drawers 27 and 28, large