What is life? This question gives a new interest to every department of science that relates to life in any form, and the history of life offers a most suggestive field for research. The paleontology took its origin in the mind of the first person who, finding something like a shell or a bone naturally imbedded in gravel or in rock, indulged in speculations upon the nature of this thing which he had dug out-this "fossil"-and upon the causes which had brought it into such a position. In this rudimentary form, a high antiquity may safely be ascribed to paleontology, inasmuch as we know that,...