When an instinct is not habit, as resulting from memory pure and simple, it is habit modified by some treatment, generally in the youth or embryonic stages of the individual, which disturbs his memory, and drives him on to some unusual course, inasmuch as he cannot recognise and remember his usual one by reason of the change now made in it. Habits and instincts, again, may be modified by any important change in the condition of the parents, which will then both affect the parent’s sense of his own identity, and also create more or less fault, or dislocation of memory, in the offspring immediately behind the memory of his last life. Change of food may at times be sufficient to create a specific modification—that is to say, to affect all the individuals whose food is so changed, in one and the same way—whether as regards structure or habit. Thus we see that certain changes in food (and domicile), from those with which its ancestors have been familiar, will disturb the memory of a queen bee’s egg, and set it at such disadvantage as to make it make itself into a neuter bee; but yet we find that the larva thus partly aborted may have its memories restored to it, if not already too much disturbed, and may thus return to its condition as a queen bee, if it only again be restored to the food and domicile, which its past memories can alone remember. So we see that opium, tobacco, alcohol, hasheesh, and tea produce certain effects upon our own structure and instincts. But though capable of modification, and of specific modification, which may in time become inherited, and hence resolve itself into a true instinct or settled question, yet I maintain that the main bulk of the instinct (whether as affecting structure or habits of life) will be derived from memory pure and simple; the individual growing up in the shape he does, and liking to do this or that when he is grown up, simply from recollection of what he did last time, and of what on the whole suited him. For it must be remembered that a drug which should destroy some one part at an early embryonic stage, and thus prevent it from development, would prevent the creature from recognising the surroundings which affected that part when he was last alive and unmutilated, as being the same as his present surroundings. He would be puzzled, for he would be viewing the position from a different standpoint. If any important item in a number of associated ideas disappears, the plot fails; and a great internal change is an exceedingly important item. Life and things to a creature so treated at an early embryonic stage would not be life and things as he last remembered them; hence he would not be able to do the same now as he did then; that is to say, he would vary both in structure and instinct; but if the creature were tolerably uniform to start with, and were treated in a tolerably uniform way, we might expect the effect produced to be much the same in all ordinary cases.