50 PRIMARY FACTORS OF ORGANIC EVOLUTION. 



tatives of the family are the lynxes, which, in some of 

 their varieties, range from Alaska to Mexico. They 

 form, however, the most northern, as well as the most 

 specialized or ' aberrant, ' type of the family. While 

 they vary greatly in color, as well as in the length and 

 texture of the pelage, at different localities, they afford 

 a most remarkable exception to all laws of variation in 

 size with locality; for a large series of skulls, repre- 

 senting localities as widely separated as Louisiana, 

 Northern Mexico, and California, on the one hand, and 

 Alaska and the Mackenzie River district on the other, 

 as well as various intermediate localities, reveals no ap- 

 preciable difference in size throughout this wide area. 

 The true cats, however, as the panther and the ocelots, 

 are found to greatly increase in size southward, or to- 

 ward the metropolis of the family. The panther ranges 

 from the Northern States southward over most of 

 South America. Skulls from the Adirondack region of 

 New York have an average length of about seveft and 

 a half inches, the length increasing to eight and three- 

 quarters in Louisiana and Texas, from beyond which 

 points there is lack of data. The ocelot {Felts partia- 

 lis) finds its northern limit near the Rio Grande of 

 Texas, and ranges thence southward far into South 

 America. The average size of Costa Rican examples 

 is about one-fifth greater than that of specimens from 

 the Rio Grande. 



Instances of increase in size northward among the 

 Carnivora of North America are so generally the rule 

 that further space need not be taken in recounting ex- 

 amples in detail. It may suffice to state that the 

 badger {Taxidea americana), the marten {Mustela ame- 

 ricana), the fisher {M. pennanti), the wolverine {Gulo 

 luscus), and the ermine {Futorius ermineus) — all north- 



