We were thus led to consider "personal identity," in order to see whether there was sufficient reason for denying that the experience, which we must have clearly gained somewhere, was gained by us when we were in the persons of our forefathers; we found, not without surprise, that unless we admitted that it might be so gained, in so far as that we once _actually were_ our remotest ancestor, we must change our ideas concerning personality altogether. We therefore assumed that the phenomena of heredity, whether as regards instinct or structure, were due to memory of past experiences, accumulated and fused till they had become automatic, or quasi automatic, much in the same way as after a long life-- . . . "Old experience doth attain To something like prophetic strain." After dealing with certain phenomena of memory, but more especially with its abeyance and revival, we inquired what the principal corresponding phenomena of life and species should be, on the hypothesis that they were mainly due to memory. I think I may say that we found the hypothesis fit in with actual facts in a sufficiently satisfactory manner. We found not a few matters, as, for example, the sterility of hybrids, the principle underlying longevity, the phenomena of old age, and puberty as generally near the end of development, explain themselves with more completeness than I have yet heard of their being explained on any other hypothesis. Most indeed of these phenomena have been left hitherto without even an attempt at an explanation. We considered the most important difficulty in the way of instinct as hereditary habit, namely, the structure and instincts of neuter insects; these are very unlike those of their parents, and cannot, apparently, be transmitted to offspring by individuals of the previous generation, in whom such structure and instincts appeared, inasmuch as these creatures are sterile. I do not say that the difficulty is wholly removed, inasmuch as some obscurity must be admitted to remain as to the manner in which the structure of the larva is aborted; this obscurity is likely to remain till we know more of the early history of civilisation among bees than I can find that we know at present; but I believe the difficulty was reduced to such proportions as to make it little likely to be felt in comparison with that of attributing instinct to any other cause than inherited habit, or memory on the part of offspring, of habits contracted in the persons of its ancestors. {127}