There are few species of American birds that have caused more perplexity to the ornithologist than the group of which _Melospiza melodia_ is the type. Spread over the whole of North America, and familiar to every one, we find each region to possess a special form (to which a specific name has been given), and yet these passing into each other by such insensible gradations as to render it quite impossible to define them as species. Between _M. melodia_ of the Atlantic States and _M. insignis_ of Kodiak the difference seems wide; but the connecting links in the intermediate regions bridge this over so completely that, with a series of hundreds of specimens before us, we abandon the attempt at specific separation, and unite into one no less than eight species previously recognized. Taking, then, the common Song Sparrow of the Eastern Atlantic States (_M. melodia_) as the starting-point, and proceeding westward, we find quite a decided difference (in a variety _fallax_) when we reach the Middle Province, or that of the Rocky Mountains. The general tints are paler, grayer, and less rusty; the superciliary stripe anteriorly more ashy; the bill, and especially the legs, more dusky, the latter not at all to be called yellow. The bill is perhaps smaller and, though sometimes equal to the average of eastern specimens, more slender in proportion. In some specimens (typical _fallax_) the streaks are uniform rufous without darker centres,—a feature I have not noticed in eastern _melodia_. Another stage (_heermanni_) is seen when we reach the Pacific coast of California, in a darker brown color (but not rufous). Here the bill is rather larger than in var. _fallax_, and the legs colored more like typical _melodia_. In fact, the bird is like _melodia_, but darker. The stripes on the back continue well defined and distinct. _M. samuelis_ (=_gouldi_) may stand as a smaller race of this variety. Proceeding northward along the Pacific coast, another form (var. _guttata_), peculiar to the coast of California, is met with towards and beyond the mouth of the Columbia (coming into Southern California in winter). This is darker in color, more rufous; the stripes quite indistinct above, in fact, more or less obsolete, and none, either above or below, with darker or blackish centres. The sides, crissum, and tibia are washed with ochraceous-brown, the latter perhaps darkest. The bill is proportionally longer and more slender. This race becomes still darker northward, until at Sitka (var. _rufina_) it shows no rufous tints, but a dusky olive-brown instead, including the streaks of the under parts. The markings of the head and back are appreciable, though not distinct. The size has become considerably larger than in eastern _melodia_, the average length of wing being 3.00, instead of 2.60.