146 



♦ KNOWLEDGE ♦ 



[May 



1887. 



more in proportion to the whole skeleton than do the same 

 bones in the wild duck, and this change may he safely 

 attributed to the domestic duck Hying much less and 

 walking much more than its wild parents.* But changes 

 which are induced in oi-gans by their use or disuse on the 

 part of the animal are not transmitted ; they die with the 

 individual in which they occur. They are powerless to 

 affect the type. It is to natural selection that we must 

 refer modifications which, appearing as relics of structure 

 common to large groups, have a specious look of being due 

 to individual use or disuse. Take, for example, the whale as 

 an illustration of this. The epitome of its ancestry which 

 the embryo presents reveals its descent from land mammals 

 having short fore and hind limbs, .scanty covering of hair, 

 broad beaver-like tails, teeth of different shape, and well- 

 developed sense organs, especially of smell. These fore- 

 fathers of the whale probably lived in marshy districts, and, 

 being omnivoi-ous, sought their food in both swamp and 

 shallow water. As conditions more and more adverse to 

 life on land supervened, they were gradually modified under 

 the action of natural selection into dolphin-like creatures, 

 living in fresh water, and at last, finding their way into the 

 ocean, from which the huge sea-lizards of earlier epochs had 

 disappeared, leaving these leviathans scope " to play therein." 

 Hence are explained the adaptive changes of structure : the 

 fore-limbs were modified into dippers enclosed in a fin-like 

 sac, but retaining the bones corresponding to like structures 

 in other mammals, as in the arm of man, the wing of the 

 bat, and the fore-leg of the horse ; whilst of the hind 

 legs traces may be detected in a few species ; the tail, 

 which acted as a powerful swimming organ, became 

 divided into two lobes ; the head became tish-like in 

 shape ; the seven bones of the neck common to most 

 mammals grew together ; the skin became hairless ; and the 

 teeth, which appear in the young whale but are never cut, 

 gave place to hanging fringes of whalebone, in the meshes 

 of which the animal entangles the minute organisms upon 

 which it feeds. In the seal, which is the modified descend- 

 ant of land flesh-feeders, the hind legs have been developed, 

 while the tail remains rudimentary. 



Of course the existing sjjecies of whales and seals are the 

 slowly modified descendants of only a small percentage of 

 ancestors, who, in virtue of their favourable adaptations to 

 altered conditions of life, survived under the operation of 

 natural selection, by which also the majority, being unfit or 

 less adapted, were weeded out. 



Natural selection, therefore, is not causal, but directive. 

 It is powerless to bring about the slightest variation in 

 plant or animal ; it is all-powerful to preserve variations 

 " beneficial to the being under its conditions of life ... it 

 can do nothing until favourable individual differences or 

 variations occur, and until a place in the natural polity of 

 the country can be better filled by some modification of some 

 one or more of its inhabitants." f Moreover, since it tends 

 to establish balance between life and its surroundings, it 

 does not imply all round development of the higher from 

 the lower. Its key-note is adaptation. To quote Herbert 

 Spencer's remarks on the erroneous conception of Evolution 

 as implying that everything has an i/itringic tendency to 

 become something higlier : " if in the case of the living 

 aggregates forming a species the environing actions remain 

 CDnstant from generation to generation, the species remains 

 constant. If those actions change, the species changes until 

 it is in adjustment with them. But it by no means follows 

 that this change in the species constitutes a .step in evolu- 

 tion. Usually neither advance nor recession results ; and 



* '• Origin o£ Species," p. 8. 



f " Origin of Species," pp. 63 and 137. 



often, certain previously-acquired structures being rendered 

 superfluous, there results a simpler form. Only now and 

 then does the environing change initiate in the organism 

 a new complication, and so produce a somewhat higher 

 type."* 



The sea-squirts and, perhaps, the marvellous rotifers, are 

 examples of recession ; actual degradation is probably limited 

 to parasites ; while in the unaltered condition of the sim- 

 plest forms .since the appearance of their earliest known 

 representatives, we have examples of persistence of type. 

 Their simplicity has been their salvation. A high organisa- 

 tion brings with it many disadvantages, for the more com- 

 plex the structure the more liable is it to get out of gear. 

 Unfortunately we cannot have highly convoluted brains, 

 and digestive organs simple and renewable as those of the 

 sea-cucumber, so that to the highest life-forms evolution is 

 not all gain. 



Variety of readjustment to altered conditions, resulting 

 in progress in some directions and in stagnation in other 

 directions, is evidenced in existing modifications of the 

 common mammalian type. AVe find one group — plant-feeders 

 — developing organs suited to their functions, as teeth for 

 grinding and large stomachs, and also acquiring organs of 

 defence or escape. In the flesh-feeders we find economy of 

 bulk, great muscular strength, and, as compared with 

 plant-feeders, prominent development of organs of attack. 

 In both groups we find progression of parts which in 

 the group including man are well nigh stationary. Among 

 the Primates limbs, teeth, and organs of digestion, have 

 all been slightly modified, and no organs of defence and 

 attack developed. The explanation is that the animals, 

 being unable to compete with the larger mammals, took to 

 an arboreal life, which induced few variations of bodily 

 structure, the most important being an opposable thumb 

 and great toe for grasping. But the need for alertness 

 against foes sharpened their wits, and the need of combina- 

 tion quickened the social instincts, so that the energy which 

 in the flesh-feeders and the plant-feeders was stored in limb 

 and muscle, was diverted in the Primates to development of 

 brain. They thus escaped the limitations of one condition, 

 which determined the development of lions and rhinoceroses 

 in a given direction, and they preserved the power to adapt 

 themselves to very diverse conditions. As shown by his 

 caieer since the earliest times that we have record of him, 

 this ^^■as markedly the case with the. apelike ancestors of 

 man. For his difference from existing apes is not in 

 bodily form ; the impassable chasm between him and them 

 lies in the superior intelligence which he possesses in virtue 

 of his more complex thinking apparatus. The arrangement 

 of the furrows of his brain is much the same as theirs, but 

 the convolutions are deeper the higher we ascend the scale, 

 the gap between the civilised man and the savage being 

 greater than that between the savage and the man-like 

 apes. 



Of the propositions expounded in the present and fore- 

 going cha])tprs this is the sum : — No two living things are 

 exactly alike. Their inherent tendency to vary is excited 

 by their surroundings, on which all life depends, and to 

 changes in which they must adapt themselves or perish. 

 Every living thing transmits its qualities, and therefore its 

 variations, to its offspring ; the more useful the variation 

 the better is the plant or animal equijjped in the struggle for 

 life. For as all living things tend to multiply so rapidly 

 that the earth would be too small in a very short time for 

 a single species, a fierce and ceaseless struggle is waged, 

 chiefly between the same species, for food and place. The 

 result is that by far the larger numbernever reach maturity, 



* '• Principles of Sociology," p. 107. 



