Insects the development of this capacity is severely limited by a funda- mental circumstance of their life history ; namely, the possession of an external chitinous skeleton by the adult creature necessitates the process of metamorphosis by which the imago is suddenly launched fullgrown upon the world to follow a mode of life radically different from that of the grub ; hence the experience of his grubby youth can be of little or no service to him, and he is called upon to shift for himself in a life that is altogether new to him ; he therefore needs to have most of his instincts in full working order from the first.

The insect is thus deprived of that period of youth under the fostering care of parents which among all the higher mammals is a principal condition of the development of such intelligence as they display.

In the young mammal the instincts ripen slowly and successively at considerable intervals; many of them come into operation only when the young creature has acquired considerable control over its bodily organs; and they are exercised in playful activities which lead to the accumulation of experience and considerable modifications of the innate dispositions, before they are needed for the carrying out of the serious tasks of life.

This period of youth, characterised by the accumulation of experience in preparation for the serious tasks of life, reaches its maximum in the most developed forms of human life, and its long duration is one of the principal conditions of all the higher developments of the human mind; the vast accumulation of experience thus rendered possible modifies so greatly the innate dispositions and their modes of operation as to obscure completely for some of us the fact of their existence ; just as in the higher mammals a lesser degree of accumulation of experience obscures in a lesser degree the nature of their innate dispositions.

If we put aside all the evidence of intelligence similar to our own in insects and other animals and consider for a moment the nature of some of their admittedly instinctive activities, it remains very difficult to under- stand how instinct as conceived by Bergson should achieve them.