SCIENCE. 



231 



special form of the manifold language of sensation. And 

 so of all the other organs of sense — they all perform their 

 work in virtue of that purely mechanical adjustment which 

 places them in a given relation to certain selected mani- 

 festations of external force, and these they faithfully trans- 

 mit, according to a code of signals, the nature of which is 

 one of the primary mysteries of Life, but the truthfulness 

 of which is at the same time one of the most certain of its 

 facts. 



For it is upon this truthfulness — that is to say, upon a 

 close and efficient correspondence between the impressions 

 of sense and certain realities of external Nature — that the 

 success of every organism depends in the battle of life. 

 And all Life involves a battle. It comes indeed to each 

 animal without effort of its own, but it cannot be main- 

 tained without individual exertion. That exertion may be 

 of the simplest kind, nothing more than the rhythmic action 

 of a muscle contracting and expanding so as to receive into 

 a sac such substances as currents of water may bring along 

 with them ; or it may be the more complex action required 

 to make or induce the very currents, which are to bring the 

 food ; or it may be the much more complex exertions re- 

 quired in all active locomotion for the pursuit and capture 

 of prey ; all these forms of exertion exist, and are all re- 

 quired in endless variety in the animal world. And 

 throughout the whole of this vast series the very life of 

 every creature depends on the unity which exists between 

 its sense-impressions and those realities of the external 

 world which are specially related to them. There is therefore 

 no conception of the mind which rests on a broader basis 

 of experience than that which affirms this unity — a unity 

 which constitutes and guarantees the various senses with 

 their corresponding appetites, each in its own sphere of 

 adapted relations to be exact and faithful interpreters of 

 external truth. 



A still more wonderful and striking proof is obtained of 

 the unity of Nature, and a still more instructive light is 

 cast upon its source and character, when we observe how 

 far-reaching these interpretations of sense are even in 

 the very lowest creatures ; how they are true not only 

 in the immediate impressions they convey, but true also 

 as the index of truths which lie behind and beyond — 

 of truths, that is to say, which are not expressly in- 

 cluded — not directly represented — in either sensation or 

 perception. This, indeed, is one main function and 

 use, and one universal characteristic of all sense-impres- 

 sions, that over and above the pleasure they give to sentient 

 creatures, they lead and guide to acts required by natural 

 laws which are not themselves objects of sensation at 

 all, and which therefore the creatures conforming to them 

 cannot possibly either see or comprehend. It is thus that 

 the appetite of hunger and the sense of taste, which in some 

 form or other, however low, is perhaps the most universal 

 sensation of animal organisms, is true not only as a guide 

 to the substances which do actually gratify the sense con- 

 cerned, but true also in its unseen and unfelt relations with 

 those demands or laws of force which render the assimila- 

 tion of new material an indispensable necessity in the main- 

 tenance of animal life. Throughout the whole kingdom of 

 Nature this law prevails. Sense-perceptions are in all ani- 

 mals indissolubly united with instantaneous impulses to 

 action. This action is always directed to external things. 

 It finds in these things the satisfaction of whatever desire 

 is immediately concerned, and beyond ihis it ministers to 

 ends of which the animal knows nothing, but which are of 

 the highest importance both in its own economy and in the 

 general economy of Nature. 



The wonderful instincts of the lower animals — the preci- 

 sion and perfection of their work — are a glorious example 

 of this far reaching adjustment between the perceptions of 

 sense and the laws which prevail in the external world. 

 Narrow as the sphere of those perceptions may be, yet 

 within that sphere they are almost absolutely true. And 

 although the sphere is indeed narrow as regards the very 

 low and limited intelligence with which it is associated in 

 the animals themselves, it is a sphere which beyond the 

 scope of their intelligence can be seen to place them in un- 

 conscious relation with endless vistas of co-ordinated ac- 

 tion. The sentient actions of the lower animals involve 

 not merely the rudimentary power of perceiving the differ- 

 ences which distinguish things, but the much higher power 



of profiting by those relations between things which are the 

 foundation of all voluntary agency, and which place in the 

 possession of living creatures the power of attaining ends 

 through the employment of appropriate means. The di- 

 rect and intuitive perception of things which stand in the 

 relation of means to ends, though it may be entirely disso- 

 ciated from any conscious recognition of this relation in it- 

 self — that is to say, the direct and intuitive perception of 

 the necessity of doing one thing in order to attain to another 

 thing — is in itself one of the very highest among the pread- 

 justed harmonies of Nature. For it must be remembered 

 that those relations between things which render them cap- 

 able of being used as means to ends are relations which never 

 can be direct objects of sensation, and therefore the power of 

 acting upon them is an intuition of something which is 

 out of sight. It is a kind of dim seeing of that which is 

 invisible. And even if it be separated entirely in the lower 

 animals — as it almost certainly is — from anything compar- 

 able with our own prescient and reasoning powers, it does 

 not the less involve in them a true and close relation 

 between their instincts and the order of Nature with its 

 laws. 



The spinning machinery which is provided in the body 

 of a spider is not more accurately adjusted to the viscid 

 secretion which is provided for it, than the instinct of the 

 spider is adjusted both to the construction of its web and 

 also to the selection of likely places for the capture of its 

 prey. Those birds and insects whose young are hatched 

 by the heat of fermentation have an intuitive impulse to 

 select the proper materials, and to gather them for the pur- 

 pose. All creatures, guided sometimes apparently by 

 senses of which we know nothing, are under like impulses 

 to provide effectually for the nourishing of their young. It 

 is, moreover, most curious and instructive to observe that 

 the extent of prevision which is involved in this process, 

 and in the securing of the result, seems very often to be 

 greater as we descend in the scale of Nature, and in pro- 

 portion as the parents are dissociated from the actual feed- 

 ing or personal care of their young. The Mammalia have 

 nothing to provide except food for themselves, and have 

 at first, and for a long time, no duty to perform beyond the 

 discharge of a purely physical function. Milk is secreted 

 in them by a purely unconscious process, and the young 

 need no instruction in the art of sucking. Birds have 

 much more to do — in the building of nests, in the choice 

 of sites for these, and after incubation in the choice of food 

 adapted to the period of growth. Insects much lower in 

 the scale of organization, have to provide very often for a 

 distant future, and for stages of development not only in 

 the young but in the nidus which surrounds them. 



There is one group of insects, well-known to every ob- 

 server — the common Gall-flies — which have the power of 

 calling on the vegetable world to do for them the work of 

 nest-building ; and in response to the means by which these 

 insects are provided, the Oak or the Rose does actually 

 lend its power of growth to provide a special nidus by 

 which the plant protects the young insect as carefully as it 

 protects its own seed. Bees, if we are to believe the evi- 

 dence of observers, have an intuitive guidance in the selec- 

 tion of food, which has the power of producing organic 

 changes in the bodies of the young, and by the administra- 

 tion of which, under what may be called artificial condi- 

 tions, the sex of certain selected individuals can be deter- 

 mined, so that they may become the mothers and queens of 

 future hives. 



These are but a few examples of facts of which the whole 

 animal world is full, presenting, as it does, one vast series 

 of adjustments between bodily organs and corresponding 

 instincts. But this adjustment would be useless unless it 

 were part of another adjustment between the instincts and 

 perceptions of animals and those facts and forces of sur- 

 rounding Nature which are related to them, and to the whole 

 cycle of things of which they form a part. In those in- 

 stinctive actions of the lower animals which involve the 

 most distant and the most complicated anticipations, it is 

 clear that the prevision which is involved is a prevision 

 which is not in the animals themselves. They appear to be 

 guided by some simple appetite, by an odor or a taste, and 

 they have obviously no more consciousness of the ends to 

 be subserved, or of the mechanism by which they are 

 1 secured, than the suckling has of the processes of nutrition. 



