being made.  Such discoveries have, it is asserted, already been made in the miocene and again in later rocks; different species of an early form of horse which are (and this we may admit) the ancestral or intermediate forms of our own horse, have been found.  I therefore would not press the difficulty, great as it is, because of the escape which the hope of future discovery always affords.  I will take this opportunity to repeat that in this chapter I say nothing about the difficulty which arises from the introduction of elementary reason or instinct, and of consciousness, into the scale of organic being; that will more appropriately fall in with the consideration of the development of man, where naturally the difficulty occurs with its greatest force.

(1) I come at once to the great difficulty that, if all existing forms are due to the occurrence of changes that helped the creature in the struggle for existence, how is it possible now to account for forms which are not advantageous? yet such forms are numerous.  Of this objection, the existence of imperfect or neuter bees and ants is an instance.  The modification in form which these creatures exhibit is of no advantage to them.  It is a great advantage, no doubt, to the other bees; but then this introduces a view of some power making one thing for the benefit of another, not a change in the form itself adapted of course to its own advantage—­since natural laws, forces, and conditions of environment could not conceivably design the advantage of another form, and cause one to change for the benefit of that other.

Why is it, again, that crabs and crayfish can only grow by casting off their shells, during which process they often die, as well as remain exposed defenceless to the attacks of enemies?  Why should stags shed their horns also, leaving them defenceless for a time?  Other animals do not do so, and there is nothing in the nature of the horn which requires it.

This brief allusion is here sufficient.  Mr. Mivart’s work gives it at large.

(2) Passing next to the question of the advantage of incomplete stages—­portions of a mechanism only useful when complete, the most striking examples may be found in the Vegetable kingdom.  The fertilization of flowering plants is effected by the pollen, a yellow dust formed in the anthers, which is carried from flower to flower.  In the pines and oaks, this is done by the wind.  But in other cases insects visit a flower to get the honey, and in so doing get covered with pollen, which they carry away and leave in the next flower visited.  Now one of our commonest and most useful plants, the red clover, is so constructed that it can only be fertilized by humble bees.  If this bee became extinct, the plant would die out; how can such a development be advantageous to it?