HETEROCHROSIS IN ESSEX BIRDS AND THEIR EGGS. 193
identification; and a Coot (Zool., 1892, p. 151), a congenital
albino with pale orange legs and red eyes, was completely
white with the exception of the crimson and yellow hair-
like processes on the head, which were as in an ordinary immature
Coot of similar age. It must be remarked, however, that a Bull-
finch (Christy) was completely white. Of the 201 Essex albinos
21 were congenital and of the latter number 14 were complete, 6
complete partial and 1 partial. In two cases, Jackdaw (Christy)
and Blackbird (Christy), the albinos shared the nest with normally
coloured birds, and in one case, Reed Bunting (B.B., v. 6, p. 61),
the young were derived from normal parents ; but four albino
House Sparrows (J. H. Owen) were descended from a white
mother. The condition of a nestling Rook (Christy) is of some
interest. In spite of the fact that it had pink eyes yet its plumage
was not wholly devoid of pigment, being cream-coloured. Only
one instance of progressive albinism appears to have been re-
corded. A female Blackbird (The Field, v. 89, p. 28) observed
first in 1893 became gradually whiter until 1897, the year of
recording. The presence of albinistic Blackbirds (E.N., v. 19,
p. 14) for a period of thirty years at the same locality can hardly
be attributed to any more likely cause than heredity.
The complete partial albinos have been described in a variety
of shades, the Rook perhaps being subject to a greater range of
colours than any other bird. The following are among the
colours assumed by the complete partials : light-cream, dark-
cream, light-dove, buff, cinnamon, brown, silver-grey, slate, drab,
dun, light-sandy and light-fawn.
The only instance of the affection of the Lesser Black-backed
Gull calls for comment. This bird was remarkable inasmuch as
one of the legs was yellow and the other flesh-coloured. It was
suggested that this might have been a hybrid between a Lesser
Black-backed and a Herring Gull. I think that it is much more
likely to be a case of albinism and therefore have included it.
The question of symmetry versus asymmetry arises. In the
first instance it is necessary to decide along what lines we shall
consider this aspect of albinism. Are the complete and complete
partials to be included or should we base our views solely on the
partials ? I have decided to follow the latter course, but unfor-
tunately, owing to lack of data, 62 out of the 109 cases being un-
described, we cannot come to a definite conclusion. However,