and plants, remarks that “we are quite unable to assign any proximate cause” for their tendency to at times reassume long lost characters. If the reader will follow for himself the remaining phenomena of reversion, he will, I believe, find them all explicable on the theory that they are due to memory of past experiences fused, and modified—at times specifically and definitely—by changed conditions. There is, however, one apparently very important phenomenon which I do not at this moment see how to connect with memory, namely, the tendency on the part of offspring to revert to an earlier impregnation. Mr. Darwin’s “Provisional Theory of Pangenesis” seemed to afford a satisfactory explanation of this; but the connection with memory was not immediately apparent. I think it likely, however, that this difficulty will vanish on further consideration, so I will not do more than call attention to it here. The instincts of certain neuter insects hardly bear upon reversion, but will be dealt with at some length in Chapter XII. V. We should expect to find, as was insisted on in the preceding section in reference to the sterility of hybrids, that it required many, or at any rate several, generations of changed habits before a sufficiently deep impression could be made upon the living being (who must be regarded always as one person in his whole line of ascent or descent) for it to be unconsciously remembered by him, when making himself anew in any succeeding generation, and thus to make him modify his method of procedure during his next embryological development. Nevertheless, we should expect to find that sometimes a very deep single impression made upon a living organism, should be remembered by it, even when it is next in an embryonic condition. That this is so, we find from Mr. Darwin, who writes (“Plants and Animals under Domestication,” vol. ii. p. 57, ed. 1875)—“There is ample evidence that the effect of mutilations and of accidents, especially, or perhaps exclusively, when followed by disease” (which would certainly intensify the impression made), “are occasionally inherited. There can be no doubt that the evil effects of the long continued exposure of the parent to injurious conditions are sometimes transmitted to the offspring.” As regards impressions of a less striking character, it is so universally admitted that they are not observed to be repeated in what is called the offspring, until they have been confirmed in what is called the parent, for several generations, but that after several generations, more or fewer as the case may be, they often are transmitted—that it seems unnecessary to say more upon the matter. Perhaps, however, the following passage from Mr. Darwin may be admitted as conclusive:—