DR. w. w. Ely's notes on chapter ii. 299 



" The symphysis of the inferior maxillary is shorter and nar- 

 rower iu the European." 



"In the structure of the molar teeth, I did not, in addition, 

 succeed in finding any difference." 



I have thus endeavored to show, from an examination of a 

 large number of skulls of the American beaver, that a greater 

 tendency to variation in these structures exists, than was observed 

 by Dr. Brandt, in the smaller number (five American and eight 

 European skulls) on which he based his differential character- 

 istics. It will be remembered that Brandt does not insist upon 

 the most obvious feature which distinguishes the Old World 

 beaver from that of the New World, viz., the greater lengthening 

 posteriorly of the nasal bones, since it "cannot be rigorously 

 proven in all cases." Following out then the principle which 

 guided his researches, many additional exceptional instances have 

 been found to invalidate the conclusion that the European and 

 the American beaver constitute different species. The extremes 

 of difference, in their aggregate, on the one side and the other, 

 are sufficiently striking to justify us in regarding them as varie- 

 ties of one and the same species; while the want of constancy 

 in these peculiarities suggests the inference, that these varia- 

 tions are due to long separation of the races, and to accidental 

 causes, rather than to original diversity of the stock. It is con- 

 ceded by the advocates of a diversity of species that the beavers 

 of the Old and the New World cannot be distinguished by any 

 external characteristic. The same is true of their habits and in- 

 stincts, except so far as they have evidently been controlled by 

 external influences. The castoreum secretion is variable, even in 

 European beavers, and there are facts to show that the elements 

 of the food of the animal are sometimes found in it. The differ- 

 ences observed in it, being more of degree than of kind, are not 

 of such a character as to render it improbable that they are due 

 to the influence of climate, food, and accidental causes. That the 

 beavers of the Old and the New World would prove fertile inter se, 

 is, from their great similarity, almost certain. The beaver is a 

 very old animal, as is proved by his fossil remains. As an 

 aquatic animal, and a vegetable feeder, it is prol)able that he lived 

 at a very early epoch, perhaps before the present configuration 

 of the continents, so that from his tendency to extensive dis- 

 tribution, and his prolific nature, there would be nothing to hinder 



