SCIENTIFIC SIDE-LIGHTS 



Activity 

 Adaptation 



to be without a Plan. The struggle for life 

 in natural selection acts with as much se- 

 lective power as does the will of man in 

 artificial selection. The latter, however, 

 acts according to a plan and consciously, the 

 former without a plan and unconsciously. 

 This important difference between artificial 

 and natural selection deserves especial con- 

 sideration. For we learn by it to under- 

 stand how arrangements serving a purpose 

 can be produced by mechanical causes act- 

 ing without an object, as well as by causes 

 acting for an object. The products of nat- 

 ural selection are arranged even more for a 

 purpose than the artificial products of man, 

 and yet they owe their existence not to a 

 creative power acting for a definite purpose, 

 but to a mechanical relation acting uncon- 

 sciously and without a plan. HAECKEL 

 History of Creation, vol. i, <ch. 11, p. 284. 

 (K. P. & Co., 1899.) 



43. ADAPTATION CERTAINLY 



KNOWN The Only Question the Method of 

 Its Production. And yet scientific men 

 sometimes tell us that " we must be very 

 cautious how we ascribe intention to nature. 

 Things do fit into each other, no doubt, as if 

 they were designed; but all we know about 

 them is that these correspondences exist, 

 and that they seem to be the result of phys- 

 ical laws of development and growth." Very 

 likely; but how these correspondences have 

 arisen, and are daily arising, is not the ques- 

 tion, and it is immaterial how that question 

 may be answered. Do those correspondences 

 exist, or do they not? The perception of 

 them by our mind is as much a fact as the 

 sight or touch of the things in w r hich they 

 appear. They may have been produced by 

 growth they may have been the result of a 

 process of development but it is not the 

 less the development of a mental purpose. 

 It is the end subserved that we absolutely 

 know. What alone is doubtful and obscure 

 is precisely that which we are told is the 

 only legitimate object of our research viz. : 

 the means by which that end has been at- 

 tained. ARGYLL Reign of Law, ch. 1, p. 20. 

 (Burt.) 



44. ADAPTATION, MUTUAL, OF DI- 

 VERSE ORGANISMS Dandelion Seed Wa- 

 ter-beetle. The structure of every organic 

 being is related, in the most essential yet 

 often hidden manner, to that of all the 

 other organic beings with which it comes 

 into competition for food or residence, or 

 from which it has to escape, or on which it 

 preys. This is obvious in the structure of 

 the teeth and talons of the tiger; and in 

 that of the legs and claws of the parasite 

 which clings to the hair on the tiger's body. 

 But in the beautifully plumed seed of the 

 dandelion, and in the flattened and fringed 

 legs of the water-beetle, the relation seems 

 at first confined to the elements of air and 

 water. Yet the advantage of the plumed 

 seeds, no doubt, stands in the closest relation 

 to the land being already thickly clothed 



with other plants, so that the seeds may be 

 widely distributed and fall on unoccupied 

 ground. In the water-beetle, the structure of 

 its legs, so well adapted for diving, allows 

 it to compete with other aquatic insects, to 

 hunt for its own prey, and to escape serving 

 as prey to other animals. DARWIN Origin 

 of Species, ch. 3, p. 71. (Burt.) 



45. ADAPTATION OF COLOR TO EN- 

 VIRONMENT -Black Cattle in Scotland- 

 Trout Colored Litye Bottom of Stream. The 

 breeders of the polled Angus a particular 

 race of black cattle in Scotland who make 

 a great point of keeping up the perfect uni- 

 formity of their blackness, getting rid of 

 every individual that has even a single 

 white foot take care to have everything 

 black about their farmsteads; all the 

 buildings are black, the horses are black, 

 the dogs are black, the fowls are black. No 

 breeder will have anything colored or white 

 about his place. Tho no account can be 

 given of the physiological action which 

 makes these precautions effective (as they 

 are asserted to be) in securing the desired 

 result, yet I am strongly inclined to think 

 that some influence of this kind is concerned 

 in producing many singular correspondences 

 between the surface-aspect of fishes and 

 Crustacea inhabiting shallow waters, and the 

 characters of the bottoms on which they 

 live. Every angler for trout is familiar with 

 variations of this kind ; and I have been as- 

 sured of cases in which these fish, when 

 transferred from one part of a stream to an- 

 other, were found in no long time to have 

 undergone a change in surface-markings, 

 which gave them the same conformity to the 

 new bottom as they previously had to the 

 old. CARPENTER Nature and Man, lect. 15, 

 p. 443. (A., 1889.) 



46. 



Shades of Color Va- 



ried in Different Surroundings. To birds 

 placed at so great a disadvantage, by a 

 feeble flight and other adverse circum- 

 stances, in the race of life, bright colors 

 would certainly prove fatal. It is true that 

 brown is not in itself a protective color, and 

 the clear, almost silky browns and bright 

 chestnut tints in several species are cer- 

 tainly not protective; but these species are 

 sufficiently protected in other ways, and can 

 afford to be without a strictly adaptive 

 color, so long as they are not conspicuous. 

 In a majority of cases, however, the color is 

 undoubtedly protective, the brown hue being 

 of a shade that assimilates very closely to 

 the surroundings. There are pale yellowish 

 browns, lined and mottled, in species living 

 amidst a sere, scanty vegetation; earthy 

 browns, in those frequenting open sterile or 

 stony places; while the species that creep 

 on trees in forests are dark brown in color, 

 and in many cases the feathers are mottled 

 in such a manner as to make them curiously 

 resemble the bark of a tree. The genera 

 lochmias and sclerurus are the darkest, the 

 plumage in these birds being nearly or quite 



