4 MICROTIN^ 



Microtus (in the wide sense understood by Miller in 1896) by 

 Vernon Bailey ^ and of Ondatra by Hollister ^ have been pubUshed 

 by the United States Biological Survey; in order to make the 

 present book as compendious as possible free use has been 

 made of this admirable work. 



Knowledge of fossil Microtinse has grown slowly since the days 

 of Buckland and Cuvier, who seem to have been the first to pay 

 attention to this part of the subject. In this country palseonto- 

 logical work on the group has been done chiefly by Owen, Sanford, 

 Blackmore and Alston, E. T. Newton, Forsyth Major and the 

 present writer; on the Continent we are indebted chiefly to 

 Pomel, Hensel, Forsyth Major, Nehring, Woldrich, and Mehely. 

 In America fossil remains have attracted less attention : Cope and 

 Hollister are the chief writers who have dealt with them hitherto. 



Mention must be made of the work of Forsyth Major and 

 Winge, two distinguished men who paid much attention to the 

 Microtinse; their respective contributions to the special hterature 

 of the group are among the most valuable we possess. In the 

 writings of Forsyth Major we find the one theory that, in my 

 opinion, fits all the facts and accounts satisfactorily for the evolu- 

 tion of rodent molars. In those of Winge is a masterly review of 

 all the mammalian orders, together with a lucid exposition of the 

 principles which should be used as a guide when investigating 

 the relationships of mammals. One may differ from Winge on 

 almost every point of detail and yet find inspiration and guidance 

 in his work. 



Every mammal is the product of two distinct and sometimes 

 conflicting forces ; a compound of relatively essential characters, 

 fixed for the time being in each group by inheritance, and of more 

 or less plastic characters which yield like potter's clay to the 

 thumb of stern necessity. It is the special use that a mammal 

 makes of its various organs that results eventually in a more or 

 less perfect adaptation of form and structure to particular func- 

 tions, no matter whether the special use is called into being by 

 tempting opportunity or by the compelUng stress of circumstances. 

 Use and habit, all that goes to make environment in the widest 

 sense, have thus made species what they are; no character is 

 absolutely beyond the reach of external influences, although in 

 practice some may never be reached. That characters so acquired 

 become in the course of generations intensified, customary, and 

 at last the normal heritable attributes of a species is the lesson 

 taught by every scrap of philosophical palseontological work upon 

 the Mammalia that has been done since the day when Kowalevsky 

 published the celebrated introduction to his memoir on Anthra- 



^ Bailey, " Revision of the American Voles of the genus Evolomys," 

 Proc. Biol. Soc. Washmgton, 11, pp. 113-138, 1897. 



Bailey, " Revision of American Voles of the genus Microtus" N. Amer. 

 Fauna, No. 17, 1900. 



2 Hollister, " A Systematic Synopsis of the Musk Rats," N. Amer. 

 Fauna, No. 32, 1911. 



