instinct to that which drove them forth a few months previously.  These remarkable changes are mainly due to the conditions of their natures, because they persist with more or less regularity under altered circumstances.  Nevertheless, they are not wholly independent of circumstance, because the period of migration, though nearly coincident in successive years, is modified to some small extent by the weather and condition of the particular year.

The interaction of nature and circumstance is very close, and it is impossible to separate them with precision.  Nurture acts before birth, during every stage of embryonic and pre-embryonic existence, causing the potential faculties at the time of birth to be in some degree the effect of nurture.  We need not, however, be hypercritical about distinctions; we know that the bulk of the respective provinces of nature and nurture are totally different, although the frontier between them may be uncertain, and we are perfectly justified in attempting to appraise their relative importance.

I shall begin with describing some of the principal influences that may safely be ascribed to education or other circumstances, all of which I include under the comprehensive term of Nurture.

ASSOCIATIONS.

The furniture of a man’s mind chiefly consists of his recollections and the bonds that unite them.  As all this is the fruit of experience, it must differ greatly in different minds according to their individual experiences.  I have endeavoured to take stock of my own mental furniture in the way described in the next chapter, in which it will be seen how large a part consists of childish recollections, testifying to the permanent effect of many of the results of early education.  The same fact has been strongly brought out by the replies from correspondents whom I had questioned on their mental imagery.  It was frequently stated that the mental image invariably evoked by certain words was some event of childish experience or fancy.  Thus one correspondent, of no mean literary and philosophical power, recollects the left hand by a mental reference to the rocking-horse which always stood by the side of the nursery wall with its head in the same direction, and had to be mounted from the side next the wall.  Another, a politician, historian, and scholar, refers all his dates to the mental image of a nursery diagram of the history of the world, which has since developed huge bosses to support his later acquired information.

Our abstract ideas being mostly drawn from external experiences, their character also must depend upon the events of our individual histories.  For example, the spoken words house and home must awaken ideas derived from the houses and the homes with which the hearer is, in one way or other, acquainted, and these could not be the same to persons of various social positions and places of residence.  The character of our abstract ideas, therefore, depends, to a considerable degree, on our nurture.