5 12 THE POPULAR SCIENCE MONTHLY. 



this is chrysolcema. In the interior of California the shore larks 

 are still smaller and redder (variety ruled), while northward and 

 coastwise appears a small lark with more streaked plumage; 

 this is strigata. All these can be generally recognized by an 

 expert ornithologist, and doubtless a closer analysis would reveal 

 the basis for still finer subdivisions.* 



In 1871 Dr. Joel A. Allen published his masterly paper on the 

 Mammals and Winter Birds of Florida. This memoir has had 

 the practical effect of making all our ornithologists, for the most 

 part against their will, believers in the theory of derivation of 

 species. 



Dr. Allen took up, as a matter of serious study, the variations 

 in individual birds. He showed that the variation of individuals 

 of the same species was far greater than had been supposed, and 

 that the characters relied on to distinguish species were often due 

 to slight increase*in these variations. For example, in Northern 

 birds the bodies would be larger, the bills smaller than in birds 

 of the same species from the South, and the coloration of birds 

 was often directly related to the degree of rainfall. He showed, 

 in brief, that each one of these many variations must be held to 

 define a distinct species, or else that the number of species of 

 American birds would have to be greatly reduced, and the range 

 of variation inside the species would need to be correspondingly 

 extended. 



This claim for attention on the part of the despised variety 

 produced much consternation among students of birds. But facts 

 must be recognized ; and the final result has been, that we have 

 now extended our idea of each species until it is large enough to 

 include all that we know of intermediate and varying forms. 

 When a hiatus appears, whether existing either in fact or in our 

 material for study, there we put our line of definition. " We can 

 only predicate and define species at all," says Dr. Coues, " from 

 the mere circumstance of missing links. Species are the twigs of 

 a tree separated from the parent stem. We name and arrange 

 them arbitrarily, in default of a means of reconstructing the 

 whole tree in accordance with Nature's ramifications." f 



* In the Auk for April, 1890, is an essay on the Horned Larks of North America, by 

 Jonathan Dwight, Jr. Mr. Dwight's conclusions are based on 2,012 specimens; those of 

 Mr. H. W. Henshaw, above given, on 350. To the forms mentioned above, Mr. Dwight 

 adds var. adusta, small, and " scorched pink '' in general hue, from southern Arizona and 

 northern Mexico ; var. menilli, large and dusky, in Idaho and neighboring regions ; and 

 var. pallidus, very small and pale, from Lower California. 



f Dr. Allen says, in a recent paper : " We arbitrarily define a species as a group of indi- 

 viduals standing out distinct and disconnected from any similar group, within which, though 

 occupying different parts of the common habitat, we recognize other forms characteristic 

 of and restricted to particular areas. These reach a maximum degree of differentiation at 

 some point in the habitat, and thence gradually shade into other con-specific forms geo- 



