“Nor seest thou yet the gathering hosts of ill
That shall en-one thee both with thine own self
And with thine offspring.”

And all this has come of admitting that a man may be the same person for two days running!  As for sopping common sense it will be enough to say that these remarks are to be taken in a strictly scientific sense, and have no appreciable importance as regards life and conduct.  True they deal with the foundations on which all life and conduct are based, but like other foundations they are hidden out of sight, and the sounder they are, the less we trouble ourselves about them.

What other main common features between heredity and memory may we note besides the fact that neither can exist without that kind of physical continuity which we call personal identity?  First, the development of the embryo proceeds in an established order; so must all habitual actions based on memory.  Disturb the normal order and the performance is arrested.  The better we know “God save the Queen,” the less easily can we play or sing it backwards.  The return of memory again depends on the return of ideas associated with the particular thing that is remembered—­we remember nothing but for the presence of these, and when enough of these are presented to us we remember everything.  So, if the development of an embryo is due to memory, we should suppose the memory of the impregnate ovum to revert not to yesterday, when it was in the persons of its parents, but to the last occasion on which it was an impregnate ovum.  The return of the old environment and the presence of old associations would at once involve recollection of the course that should be next taken, and the same should happen throughout the whole course of development.  The actual course of development presents precisely the phenomena agreeable with this.  For fuller treatment of this point I must refer the reader to the chapter on the abeyance of memory in my book Life and Habit, already referred to.

Secondly, we remember best our last few performances of any given kind, so our present performance will probably resemble some one or other of these; we remember our earlier performances by way of residuum only, but every now and then we revert to an earlier habit.  This feature of memory is manifested in heredity by the way in which offspring commonly resembles most its nearer ancestors, but sometimes reverts to earlier ones.  Brothers and sisters, each as it were giving their own version of the same story, but in different words, should generally resemble each other more closely than more distant relations.  And this is what actually we find.