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nection with facts manifestly abating the struggle for existence. In view of this problem Dr. Hooker has said,—" The adjustment of the parts of the flower to the form and habits of the insect or bird, and of these to the flower, is so accurate, that it is in vain to speculate whether the plant was adapted to feed the animal, or the animal adapted to fertilize the plant." * This suggestion of the needlessness of speculation is natural from a scientific point of view, and we may do well to remember the warnings against risks attending the search for final causes, which have been sounded from the days of Spinoza to the present time; but there is a problem here which science can not leave in abeyance. The facts are undoubted, and the natural causes must be sought. The parts of the flowers are adapted to the forms and habits of the insects; the insects are adapted to the work of fertilizing the plants; the question is, How are these two things secured? The inquiry which has awakened general interest as to the development of species in the history of distinct orders such as orchids, insects, pig
* Botany, (Science Primers) by Dr. J. D. Hooker, C.B., P.R.S., p. 79.
eons, and dogs, must strive to complete its work, by pressing on to this more complicated question concerning the adaptation of distinct organisms to influence and aid each other in the work of development. In what way science may deal with this question, and how far it may be able to advance in the search for an answer, it may be difficult to decide. For it is much easier to indicate the logical necessity for an advance, than to say in what manner the advance is to be accomplished. The one is a simple question of logical requirement; the other must be a matter of continued observation, and scientific inference. Whether science may yet discover an answer; or whether it may prove true at this point, as at other points already mentioned, that science has here reached clear marks of its own limits, must be left to the future, to be determined by those devoted to scientific research. As long, however, as this question of interdependence remains without a scientific explanation, it must be obvious that there are important facts which seem to imply some modification of the theory of descent, or evolution of species by means of selection, under the severe struggle for existence. Or, to put it from another point of view, nature has marvellously provided for mitigation of the struggle for existence, by contrivances providing both for vegetable and animal life; therefore the theory of the origin and development of life which depends chiefly on the struggle for existence must be adjusted to allow for a theory of the effects arising from the natural provision for obviating the strug'gle, and providing for a large increase of life. Quite beyond this, as a matter entirely distinct, is the question as to the primordial forms of existence in the history of plants and insects. As to this, science may be able to give very little testimony, as it is a question of the remote past, on which present facts may afford little evidence. Still, beyond these primordial forms, in a region which science can not enter, there lies the question of origin, of actual beginning, creation of life, as to the reality of which science can speak only indirectly by discovery of its own limits, in the terms of its ultimatum, nature has provided that such and such things shall be.
Before leaving the department of insect life, there is a collateral and complementary series of observations, bearing upon the nature and activity of Ants, which deserves attention. The ants are a race of insects as diligently industrious as the bees, like them also fond of honey and of all sweet substances; but unlike them ready to devour other insects. Along with the industry of the bee, they have predatory tendencies, leading them into conflict with other races, or even involving different orders of their own race in warfare. It is a curious fact, in this connection, that many of the flowering plants have contrivances which guard them from the approach of ants. Creeping insects find the way barred against them while the flying insect at once and easily reaches the stores of honey, not knowing any thing of the difficulties in the path of the less favored rival. Spikes grow with their points in a downward direction, against which no creeping insect can make way; waxy or glutinous matter is spread over the leaves, which insects shun as a trap; and there are velvety flexible leaves from the edge of which the insect easily slips off. Special attention has been turned to this field of research by Kerner,* an interesting outline of the results of
his observations being given by Sir John Lubbock.* The conclusion reached as to the utility of these contrivances for exclusion of creeping insects, is that they perform an auxiliary part in the general plan for fertilization which has been described. To allow the store of honey to go to the ants would be merely to feed them without any equivalent advantage to the flowers. To diminish the supply in this way, might cause the bees to abandon many flowers, and so greatly diminish fertilization. This would ultimately lead to short supplies, and probable extinction of several orders of plants and animals, and accordingly these contrivances to hinder the access of ants, must be added to those for facilitating the approach of bees, and other flying insects, affording further evidence of the adjustment of rival interests involved in the relations of the vegetable and animal kingdoms. The serried spikes are a phalanx of bayonets planted for resistance of an advancing foe.
Contemplating now the ants as in some respects an excluded race, which with a large share of pugnacity can not find a basis of op erations for contending against the bees, we
* Scientific Lectures, p. 36.