“Even without any change in the proportional numbers of the animals on which our wolf preyed, a cub might be born with an innate tendency to pursue certain kinds of prey.  Nor can this be thought very improbable; for we often observe great differences in the natural tendencies of our domestic animals:  one cat, for instance, taking to catching rats, another mice; one cat, according to Mr. St. John, bringing home winged game, another hares or rabbits, and another hunting on marshy ground!, and almost nightly catching woodcocks or snipes.  The tendency to catch rats rather than mice is known to be inherited.  Now, if any slight innate change of habit or of structure benefited an individual wolf, it would have the best chance of surviving and of leaving offspring.  Some of its young would probably inherit the same habits or structure, and by the repetition of this process a new variety might be formed which would either supplant or coexist with the parent-form of wolf.  Or, again, the wolves inhabiting a mountainous district, and those frequenting the lowlands, would naturally be forced to hunt different prey; and from a continued preservation of the individuals best fitted for the two sites, two varieties might slowly be formed.  These varieties would cross and blend where they met; but to this subject of intercrossing we shall soon have to return.  I may add that, according to Mr. Pierce, there are two varieties of the wolf inhabiting the Catskill Mountains in the United States, one with a light greyhound-like form, which pursues deer, and the other more bulky, with shorter legs, which more frequently attacks the shepherd’s flock.”—­(pp. 90, 91.)

We eke out the illustration here with a counterpart instance, viz., the remark of Dr. Bachman that “the deer that reside permanently in the swamps of Carolina are taller and longer-legged than those in the higher grounds.” [I-10]

The limits allotted to this article are nearly reached, yet only four of the fourteen chapters of the volume have been touched.  These, however, contain the fundamental principles of the theory, and most of those applications of it which are capable of something like verification, relating as they do to the phenomena now occurring.  Some of our extracts also show how these principles are thought to have operated through the long lapse of the ages.  The chapters from the sixth to the ninth inclusive are designed to obviate difficulties and objections, “some of them so grave that to this day,” the author frankly says, he “can never reflect on them without being staggered.”  We do not wonder at it.  After drawing what comfort he can from “the imperfection of the geological record” (Chapter ix), which we suspect is scarcely exaggerated, the author considers the geological succession of organic beings (Chapter X), to see whether they better accord with the common view of the immutability of species, or with that of their slow and gradual modification.  Geologists must settle that question.  Then follow two most interesting and able chapters on the geographical distribution of plants and animals, the summary of which we should be glad to cite; then a fitting chapter upon classification, morphology, embryology, etc., as viewed in the light of this theory, closes the argument; the fourteenth chapter being a recapitulation.