In these earliest lectures he sounded the note of which his last public utterance was the dying cadence. For, as this biography rightly intimates, his scientific life was singularly entire and homogeneous--if not uninfluenced, yet quite unchanged, by the transitions which have marked the period. In a small circle of naturalists, almost the first that was assembled to greet him on his coming to this country, and of which the writer is the sole survivor, when Agassiz was inquired of as to his conception of "species," he sententiously replied: "A species is a thought of the Creator." To this thoroughly theistic conception he joined the scientific deduction which he had already been led to draw, that the animal species of each geological age, or even stratum, were different from those preceding and following, and also unconnected by natural derivation. And his very last published works reiterated his steadfast conviction that "there is no evidence of a direct descent of later from earlier species in the geological succession of animals." Indeed, so far as we know, he would not even admit that such "thoughts of the Creator" as these might have been actualized in the natural course of events. If he had accepted such a view, and if he had himself apprehended and developed in his own way the now well-nigh assured significance of some of his early and pregnant generalizations, the history of the doctrine of development would have been different from what it is, a different spirit and another name would have been prominent in it, and Agassiz would not have passed away while fighting what he felt to be--at least for the present--a losing battle. It is possible that the "whirligig of time" may still "bring in his revenges," but not very probable.