But an instinct within him tells him that this cannot be the last word as to Nature's character and methods. He himself is constantly risking his life with no thought of trying to survive, and he sees his neighbours doing the same. And his inclination is to go a good deal farther than tamely adapting himself to his surroundings. He wants and strives to rise superior to them—and he finds his neighbours likewise striving. So with this instinct goading him on he is driven to probe deeper still into the mystery of the forest life.
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Of selection and adaptation we have seen evidence throughout the whole forest life. Now, where there is selection and where there is adaptation there must be purposiveness. Selection implies the power of choice, and we have seen how plants as well as animals deliberately and effectively exercise this power of choice. And adaptation implies adjustment to an end, and we have seen how wonderfully plants no less than animals adapt themselves to certain ends. And where individuals have the power of choice and exercise that power; and where they have the power of adapting themselves to certain ends and exercise that power, there obviously is purposiveness.
Purposiveness runs like a streak through every activity. It permeates the whole forest life. It is observable in plants no less than in animals. Naturalists, indeed, regard trees and plants as truly sentient beings. And the means plants employ to compass the end they have in view, are truly wonderful. Still more remarkable is the fact that hardly two attain their object by exactly the same means. The tropical forest is full of climbing plants bent upon reaching the sunlight. But some climb by coiling round the trunk of a tree like a snake, some swarm up it by holding on with claws, some ascend by means of adhering aerial roots, and some reach what they want by pushing through a tangle of branches spreading out arms and hauling themselves up. And when plants have attained maturity and flowered, the flowers employ numberless ways of attracting insects for the purpose of fertilisation. In a still, tropical forest, such as that of Lower Sikkim, there is no hope of the pollen being carried from one flower to another by air-currents. The flowers have therefore to devise a means for the transport of the pollen. Efforts are made to induce winged creatures—insects in most cases, but sometimes birds—to render assistance. Colours for day-flying insects and scent for night-flying insects are accordingly employed as means to this end. Brilliant colours attract butterflies and bees by day. Strong scent—sometimes pleasant to our taste, sometimes the reverse—attracts moths and other insects by night. And the flowers which depend on their scents and not on colour are usually white or dull brown or green. And this scent is not exhaled when it is not needed, but only when the insects which the flowers wish to attract are about.
Orchids especially seem to know what they want. Their aerial roots wander about in search of what they want and seem to smell their way. They use discrimination in utilising their knowledge. They choose. And each individual seems to choose in its own way. From among many means of achieving the same end they make a definite choice, and different plants make different choices—they use different means.
Plants, therefore, quite evidently employ means to an end. They have an end in view—sometimes their own maintenance, sometimes the perpetuation of their kind, sometimes something else—and they employ means to achieve that end. They are, that is to say, purposive in their nature.
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Evidence of purposiveness is also furnished by the wonderful organs of adaptation, root-tips, leaves, eyes, lungs, etc. It is extremely improbable that they came into being—or even started to come into being—by mere chance alone. The odds are countless millions to one against the atoms, molecules, and cells—myriads in number—of any one of these organs of adaptation having by mere chance grouped themselves in such a way as to form an effective eye, or lung, or leaf. It is, literally speaking, infinitely improbable that the organs of adaptation we see in a forest, in plant and animal, should have come into existence through chance alone.
The organs of adaptation are distinctly and definitely purposive structures—not purposed, perhaps, but certainly purposeful. In its struggle with its surroundings and with competitors the individual has been compelled to bring into being organs to fulfil a purpose. It is not the case that the organ was first created and then a use found for it, or use made of it. What actually happens is that first there is a vague but insistent reaching out towards an end, towards the fulfilment of some inner want or need—the need for food or to propagate, or whatever it may be—and that to achieve that end, or fulfil that need, the individual is driven to create a special organisation—as an Air Ministry was created during the War to fulfil the new need for fighting in the air—and so a new organ is produced: an essentially purposive structure such as the eye or the lung, though unpurposed before the need arose. The organs we see, therefore, are outward and visible signs of the existence within of a definite striving towards an end—that is, of a purpose.
The forest shows an abundant, varied, and intense life in which individuals are for ever battling with one another. But all is not happening by chance. Everywhere we see signs of purposiveness. Purposiveness—the striving towards an end—stands out as a dominating feature in forest life. Selections and adaptations are made, but they are made with some purpose in view. Purpose governs the adaptations and selections. What that purpose is we shall try and discover as we get to know still more of Nature.