The last five chapters of the book are devoted to the discussion of certain subjects of vital interest and great moment just now in the scientific world--the theories of progression, development, transmutation, and variation of species. It seems, however, to be the intention of the author to give us, not so much his own views as a general resume or outline of the tendencies and conclusions of the scientific world upon these subjects. This he does with his usual fulness, candor, and impartiality; and the reader at the same time gathers from him that he is strongly inclined to accept the doctrine of the origin of species by 'variation and natural selection,' and to accord vast periods of time for the workings of that law of development and transmutation which he believes to pervade all mundane affairs. Considerable space is devoted to the consideration of man's place in nature, and especially to the discussions arising out of the comparison of the human and simian brain; and while the author fully admits the vast gulf placed between man and the animal creation below him--a gulf which science cannot bridge--by virtue of the moral and religious nature of man, yet he pointedly protests against confounding distinct orders of ideas, and insists that man as a physical being is clearly of the same order as the gorilla and ape; and he does not shrink from accepting the possibility that they all may have sprung by successive stages or 'leaps' from the same primordial form. His concluding words are, that 'so far from having a materialistic tendency, the supposed introduction into the earth at successive periods of life--sensation, instinct, the intelligence of the higher mammalia, bordering on reason--and lastly the improvable reason of man himself, presents us with a picture of the ever-increasing dominion of mind over matter.' To our mind one thing is certain. The whole scientific world is drifting slowly, but steadily and surely, to the verification and acceptance--with certain and in some cases important modifications--of the development hypothesis of Maillet, Lamarck, La Place, Owen, and the author of the 'Vestiges[4] of Creation.' The movement reminds one of the motion of one of the great Greenland glaciers, so slow, quiet, almost imperceptible, yet inexorable as fate--heedless of all obstacles. As in the case of all great, genuine revolutionary or formative ideas, it is curious to watch the incidents of its career--to note the alarm, indignation, scorn, and holy horror occasioned by its first announcement--to observe these subsiding gradually into patient endurance and permissive sufferance, and these again giving place to a certain curiosity and wakeful interest, culminating at last in downright advocacy and championship.