Page:Popular Science Monthly Volume 37.djvu/527

Rh variation, which, however, is pleasant to me as a specialist, though odious as a systematist. . . . How painfully true is your remark that no one has hardly a right to examine the question of species who has not minutely described many!... Certainly I have felt it humiliating, discussing and doubting and examining, over and over again, when in my mind the only doubt has been whether the form varied to-day or yesterday. . . . After describing a set of forms as distinct species, tearing up my manuscripts and making them one species, tearing that up and making them separate, and then making them one again (which has happened to me), I have gnashed my teeth, cursed species, and asked what sin I had committed to be so treated."

An epoch in systematic zoölogy began with the study of the collections made by the United States Pacific Railway Survey some thirty years ago. This was the first opening out to naturalists of the details of the fauna of a vast district under the same parallels of latitude, but showing every variation in rainfall, elevation, and physical surroundings. The most valuable results of these collections were seen in the study of birds. It was found in general that each bird of the Atlantic States had its counterpart in the prairies, the sage-plains, the mountains, and the Pacific slope. Differences were carefully sought for and found, for the school of Prof. Baird allowed nothing to escape their analysis. There were differences in size, in form and color, slight in degree, but nevertheless really existing, and these were made the basis of as many distinct species. Still further studies increased the number of these species, until at last a large proportion of our birds were represented by Eastern, Western, sage-brush, and prairie species. Sometimes these closely connected forms were distinguishable at first sight, as in the case of the yellowhammer, and its double, the red-shafted flicker; in other cases baffling the most skillful, as with the two species of the crow-blackbird.

An illustration of these forms and their relations may be taken from the common shore lark and its varieties, although it is fair to say that some of these variations have never been regarded as species.

The shore lark, or horned lark (Otocoris alpestris), ranges widely over the colder and open parts of Europe, Asia, and America. The common form, called alpestris, is familiar to most of us. In the Northwestern region, as far south as Utah, is another form, equally large, but paler in color (eucolæma). In the prairie region the lark is of the ordinary color, but smaller (praticola). In the sage-plains, it is a similarly small but pale lark, with brighter yellow in its throat; this is arenicola. In Texas the bird is still smaller and grayer (giraudi); while the small form found in New Mexico and Arizona has its plumage strongly washed with red;