The Descent of Man

Macgillivray, 'History of British Birds,' vol. iii.
p. 745, 'Ibis,' vol. v. 1863, p. 469.) This case
seems analogous to that lately given of albino
birds not pairing from being rejected by their
comrades.
In various parts of the northern seas a remarkable
variety of the common Guillemot (Uria
troile) is found; and in Feroe, one out of every
five birds, according to Graba's estimation, presents
this variation. It is characterised (41. Graba,
ibid. s. 54. Macgillivray, ibid. vol. v. p. 327.)
by a pure white ring round the eye, with a curved
narrow white line, an inch and a half in
length, extending back from the ring. This
conspicuous character has caused the bird to be
ranked by several ornithologists as a distinct
species under the name of U. lacrymans, but it
is now known to be merely a variety. It often
pairs with the common kind, yet intermediate
gradations have never been seen; nor is this
surprising, for variations which appear sud-