GUILLEMOT, or, as it is usually called in U.S.A., MURRE, a sea-bird breeding on the rocky coasts of the North Atlantic in vast numbers. This bird, Uria aalge, is a member of the auk family and, like the rest of the Alcidae, it winters in the open sea. A second species, Brunnich's Guil lemot (U. lomvia), inhabits the Atlantic coasts of North America with U. aalge. Other species occur farther northward, on the west coast of North America and elsewhere. The black guillemot, U. grylla, known to sailors as the doveky, is almost entirely black in summer plumage. Unlike the common f orm, which lays a single egg, the black guillemot pro duces two or three in a clutch. The so-called bridled or ringed guillemot is a variety of U. aalge with a white mark resembling a bridle round its eye. It is worth mention as a good example of a quite distinct variation found in considerable numbers in nature, but not intergrading with the normal. It is probably due to a Mendelian mutation.