394 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 192 8 



of mammals in the study of bacteriology, in experiments on the 

 transmission of disease, in investigating the relation of foods and 

 the glands of internal secretion to bodily development, and in at- 

 tempting to solve the enigmas of psychology, heredity, speciation, 

 isolation, and relation to environment. In all of this study an exact 

 knowledge of the specific identity of each animal under observation 

 is needed. Gradually it is being learned that species which are 

 nearly allied may, nevertheless, *react quite differently to a given 

 stimulus, such as heat, cold, hunger, or exposure to disease. A pri- 

 mary requirement in experimentation is therefore to know precisely 

 what kind of mammal is being used by every worker in the field, so 

 that results may be accurately compared. The specialist in bacteri- 

 ology, in psychology, or in genetics is unable to supply this informa- 

 tion himself; he must go to the mammalogist for it; and in so doing 

 he furnishes one more example of the way in which human advance- 

 ment is linked up with the seemingly unimportant pursuit of sys- 

 tematic study carried on for the intellectual satisfactions which it 

 brings. 



Turning from these practical matters to the more theoretical as- 

 i:)ccts of zoology we find conspicuous instances in which generaliza- 

 tions have gone astray for lack of this fundamental knowledge. The 

 following are two good illustrations. 



Darwin observed that the wijd rabbits inhabiting the islet of 

 Porto Santo, one of the Madeira Islands, were smaller than those of 

 England. Knowing that the Porto Santo rabbits had been introduced 

 by the Portuguese about the year 1419, he concluded that a decrease 

 of " nearly 3 inches in length and almost half in weight of body " 

 had taken place in four and one-half centuries. As it was supposed 

 in Darwin's time, and for half a century later, that all the wild 

 rabbits of Europe belonged to a single race, this conclusion as to the 

 animals on the island seemed justified, and the story of the Porto 

 Santo rabbit found its way into many treatises on evolution. But 

 subsequent systematic study of the rabbits showed that there are in 

 reality two races, a large one in central Europe and a smaller one in 

 the Mediterranean region and the Iberian Peninsula. Being unaware 

 of this fact, Darwin compared the Porto Santo rabbit with the wrong 

 animal and so arrived at a false conclusion which has been given 

 Avide circulation in popular textbooks. Recently a German author 

 was engaged on the problem of the changes which have taken place 

 in mammals under the influence of domestication. He believed that 

 domestication tends to bring about marked changes in the form of 

 the skull. As his most striking example of such a change he com- 

 pared the skull of the domestic ferret with that of the wild European 

 polecat. He had no difficulty in finding conspicuous differences, 

 which are clearly apparent in his published photographs of the two 



