_Eggs._--[AUTHOR'S NOTE: The black-and-white warbler usually lays 4 or 5 eggs to a set, normally 5, seldom fewer or more. These are ovate to short ovate and slightly glossy. The ground color is white or creamy white. Some are finely sprinkled over the entire surface with "cinnamon-brown," "Mars brown," and "dark purplish drab"; others are boldly spotted and blotched with "russet" and "Vandyke brown," with underlying spots of "brownish drab," "light brownish drab," and "light vinaceous-drab." Speckled eggs are commoner than the more boldly blotched type. The markings are usually concentrated at the large end, and on some of the heavily spotted eggs there is a solid wreath of different shades of russet and drab. The measurements of 50 eggs average 17.2 by 13.3 millimeters; the eggs showing the four extremes measure =18.8= by 13.7, 17.9 by =14.7=, =15.7= by 12.7, and 16.3 by =12.2= millimeters (Harris).] _Young._--Cordelia J. Stanwood (MS.) speaks of the nestlings a few days from the egg as "very dark gray, much like young juncos and Nashville warblers." But when they leave the nest they are clearly recognizable as young black-and-white warblers, although they are slightly tinged with brownish. By mid-July, here in New England, they assume their first winter plumage, and, as both sexes of the young birds have whitish cheeks, they resemble very closely their female parent. Unlike the young of some of the other warblers which remain near the ground for many days, the young black-and-white warblers shortly ascend to the branches of trees where they are fed by the old birds. I find no definite record of the length of the incubation period, but in a nest I watched in 1914 it was close to 10 days. Burns (1921) gives the period of nestling life as 8 to 12 days. _Plumages._--[AUTHOR'S NOTE: Dr. Dwight (1900) calls the natal down mouse gray, and describes the juvenal plumage as follows: "Above, wood-brown streaked with dull olive-brown, the upper tail coverts dusky; median crown and superciliary stripe dingy white. Wings and tail dull black, edged chiefly with ashy gray, the tertiaries (except the proximal which is entirely black) broadly edged with white, buff tinged on the middle one. Two buffy white wing bands at tips of greater and median wing coverts. The outer two rectrices with terminal white blotches of variable extent on the inner webs. Below, dull white, washed on the throat and sides with wood-brown, obscurely streaked on throat, breast, sides and crissum with dull grayish black."