of the Pleistocene and the present age.  Now it is further true that each one of these types is represented today in the mature antlers of existing deer, from the small South American species with a simple spike, up to the wapiti and red deer carrying six or eight points, and still more significant is it that the whole story is recapitulated in the growth of each individual of the higher races.  The earliest cervine animals known seem to have had no antlers at all, a stage to which the fawn of the year corresponds; the subsequent normal addition in the life-history, of a tine for each year of growth until the mature antler is reached, answering with exactness to the stages of advance shown in the development-history of the race.  A year of individual life is the symbol of a geological period of progression.  This is a marvelous record, of which we may say—­paraphrasing with Huxley the well-known saying of Voltaire—­“if it had not already existed, evolution must have been invented to explain.”

The least technical, and for the present purpose the most useful of the characters distinguishing existing deer from all of the bovine stock, lies in the antlers, which are solid, of bony substance, and are annually shed.  They are present in the males of all species except the Chinese water deer, and the very divergent musk-deer, which probably should not be regarded as a deer at all.  They are normally absent from all females except those of the genus Rangifer.  Most deer have canine teeth in the upper jaw, though they are absent in the moose, in the distinctively American type and a few others.  The cleaned skull always shows a large vacuity in the outer wall in front of the orbit, which prevents the lachrymal bone from reaching the nasals.  No deer has a gall bladder.  There are many other distinctions, but as all have exceptions they are of value only in combinations.

The earliest known deer, belonging to the genus Dremotherium, or Amphitragulus, from the middle Tertiary of France, were of small size and had four toes, canine teeth and no antlers.  Their successors seem to have borne simple forked antlers or horns, probably covered with hair, and permanently fixed on the skull.  Very similar animals existed in contemporaneous and later deposits in North America.  From this point the course of progress is tolerably clear as to deer in general, although we are not sure of all the intermediate details—­for it must not be forgotten that a series of types exhibiting progressive modifications in each succeeding geological period is quite as conclusive in pointing out the genealogy of an existing group as if we knew each individual term in the ancestral series of each of its members.  Thus we do not yet know whether the peculiar antler of the distinctively American deer, of the genus Mazama, is derived from an American source or took its origin in the old world, for the fossil antlers known as Anoglochis,