"The products of what are commonly called physical agents are everywhere the same, (that is, upon the whole surface of the globe,) and have always been the same (that is, during all geological periods); while organized beings are everywhere different, and have differed in all ages. Between two such series of phenomena there can be no causal or genetic connection. "The combination in time and space of all these thoughtful conceptions exhibits not only thought, it shows also premeditation, power, wisdom, greatness, prescience, omniscience, providence. In one word, all these facts in their natural connection proclaim aloud the One God, whom man may know, adore, and love; and Natural History must, in good time, become the analysis of the thoughts of the Creator of the Universe, as manifested in the animal and vegetable kingdoms." To this statement we must add two paragraphs from the pages just preceding, (pp. 130, 131.) "If I have succeeded, even very imperfectly, in showing that the various relations observed between animals and the physical world, as well as between themselves, exhibit thought, it follows that the whole has an Intelligent Author; and it may not be out of place to attempt to point out, as far as possible, the difference there may be between Divine thinking and human thought." "Taking nature as exhibiting thought for my guide, it appears to me, that, while human thought is consecutive, Divine thought is simultaneous, embracing at the same time and forever, in the past, the present, and the future, the most diversified relations among hundreds of thousands of organized beings, each of which may present complications, again, which to study and understand even imperfectly, as, for instance, man himself, mankind has already spent thousands of years. And yet, all this has been done by one Mind, must be the work of one Mind only, of Him before whom man can only bow in grateful acknowledgment of the prerogatives he is allowed to enjoy in this world, not to speak of the promises of a future life." Chapter Second is entitled, "Leading Groups of the existing systems of animals." Its nine sections treat successively of the great types or branches of the animal kingdom, of classes, orders, families, genera, species, other natural divisions, successive development of characters, and close with some very significant conclusions on the importance of the study of classification. Mr. Agassiz has attempted to give definiteness to the terms above enumerated, which have been used with various significance, by limiting each one of them to covering a single category of natural relationship. Thus:-- _Branches_ or _types_ are characterized by their plan of structure. _Classes_, by the manner in which that plan is executed, so far as ways and means are concerned. _Orders_, by the degrees of complication of that structure. _Families_, by their form, so far as determined by structure.