Wolves, varieties of, [90].

Woodpecker, habits of, [184].

——, green colour of, [197].

Woodward, Mr., on the duration of specific forms, [294].

——, on the continuous succession of genera, [316].

——, on the succession of types, [339].

World, species changing simultaneously throughout, [322].

Wrens, nest of, [243].

Y.

Youatt, Mr., on selection, [31].