the subject, to extend the field of view somewhat further 

 into the past, summarizing briefly some portions of the 

 paper already cited. Beginning then with what may be 

 termed the Bairdian period we may trace in outline the 

 history of the subject as regards (i) methods, (2) resources, 

 and (3) results. 



(1.) Methods.— From 1850 to about 1865 the chief incent- 

 ive to research in this field was apparently the discovery of 

 new forms. The subjects of individual and seasonal 

 variation were to a large extent necessarily neglected ; 

 their importance even had not come to be duly appreci- 

 ated, there being rarely available for study a series of 

 specimens of any species of sufficient extent to throw much 

 light upon either of these questions. Neither was much 

 attention paid to the equally important subject of geo- 

 graphic variation, for the very good reason that adequate 

 material for its investigation did not exist. Accordingly 

 very slight differences, especially if accompanied by a 

 difference of habitat in the specimens presenting them, 

 were regarded as of specific importance. The word sub- 

 species, in its modern sense, was an unknown term in bi- 

 ologic terminology. 



Following Baird's work, done mainly between 1852 and 

 1858, was a considerable interval of almost complete in- 

 activity. There was, it is true, a gradual increase of ma- 

 terial in a few of the principal museums, notably that under 

 the direction of the Smithsonian Institution, but little was 

 done toward its elaboration between the years i860 and 

 1870. 



At about this later date new workers entered the field, 

 and with the greatly increased material at their disposal it 

 became possible to take up, in the case of a few species, 

 the neglected subjects of individual, seasonal, and geo- 

 graphic variation. It was found that many differences — as 

 of size, color, and even in the relative size of different 

 parts — which had previously been depended upon as of 

 specific importance, were open to suspicion. These dis- 



