EVOLUTION AND DISTRIBUTION OF ANIMALS. 511 



founded variation, •which, however, is pleasant to me as a special- 

 ist, 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 describ- 

 ing 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 zoology 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 natural- 

 ists of the details of the fauna of a vast district under the same 

 parallels of latitude, but showing every variation in rainfall, ele- 

 vation, 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 {Jeucolcemd). In the prairie 

 region the lark is of the ordinary color, but smaller (praticoTa). 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 ; 



