630 ANNUAL REPOET SMITHSONIAN INSTITUTION, 1917. 



inheritance in the fly, Drosophila; but, as Dr. L. O. Howard has 

 written, " knowing that there are more than 50 species of DrosoyhiJa 

 in the United States, it gives me an idea of inexactness when I see 

 so many of these papers in which no species is mentioned. The 

 writers seem to be entirely indifferent on this point" (Science, 25th 

 Jan., 1918). In view of the curious differences in habit, mode of re- 

 production and development, physiological chemistry, and the like 

 that obtain between species of closely similar external appearance, it 

 should be plain that the most rigid determination of the material 

 under experiment or observation is the first step on which the rest 

 depends. The worker who omits this precaution is like a chemist cal- 

 culating atomic weights from salts bought at a cheap drug store. 



Wliat is true of the purely biological sciences applies also to vari- 

 ous branches of geology and anthropology, using those terms in their 

 widest possible sense. Modern stratigraphy, with which is intimately 

 related tectonic geology, leading on to dynamical geology and the vast 

 sweep of cosmogony, depends more and more on minute discrimina- 

 tion between the successive mutations of life forms and the study of 

 their geographical wanderings. Here the museum systematist and 

 the field geologist must cooperate, the latter by extensive and in- 

 tensive collecting of fossils, the former by accumulating material 

 from all horizons and regions into one place for direct comparison 

 and intimate scrutiny. If petrolog}^ must be studied first in the field 

 and the laboratory, it is the museum that must preserve for reference 

 a standard series of rocks and minerals, rough-hewn, polished, weath- 

 ered, in hand specimens, and in thin sections, representing all local- 

 ities and the varied modes of occurrence. The ethnologist who frames 

 hypotheses of migration without a comparative study of material 

 coming from all parts of the world and illustrating distinct branches 

 of human activity is bound to fall into error ; it is only in museums 

 that such a study can be made. The dependence of the archeologist 

 on museums is no less obvious, but even the historian of later days 

 would frequently avoid mistakes if he would make himself more 

 familiar with the concrete evidence preserved in our museums, often 

 a surer witness than documents colored unconsciously or with intent 

 by the prejudices of their writers. Thus, in the hands of Mr. A. W. 

 Pollard, the technical details of certain printed books have thrown 

 on the history of religious toleration, of the liberty of the press, and 

 of the theater in this country, a clearer light than was afforded by 

 existing written statements. Or, again, the history of the scattered 

 Greek communities from 700 to 300 B. C. is wonderfully elucidated 

 by the history of their coinage which Prof. Percy Gardner has just 

 published. And, as the Times puts it, " without the stately array of 

 volumes which form the British Museum Catalogue of Coins," the 

 latter history " could not be attempted." 



