236 



KNOWLEDGE. 



[October, 1902. 



rosonibles A;/, riirunn's in a remarkable way and grows 

 ill (ho saino situations. Botli liavc the identical odour 

 of decaying fish, but as the spores of the former are red, 

 while those of the latter ai-e white, they are classified 

 in distinct and separate groups. 



It has frequently been asserted that the spores of the 

 lonimon mushroom do not germinate unless they have 

 been swallowed by some warm-blooded animal. Although 

 this is denicfl by competent authorities, the fact remains 

 that agai-ics are eaten by horses, cattle, sheep, squirrels 

 and other animals. The partiality of certain fuugi for 

 animal droppings also favours the id^a that some species 

 at least are benefited in this way. On this assumption 

 a poisonous species would profit by its resemblance to 

 an edible species. On the other hand a conspicuous 

 species with unwholesome properties might afford a 

 model which edible species might copy with advantage, 

 if their spores were incapable of withstanding the action 

 of digestive fluids. 



It is held by some that the function of the cystidia 

 which occur along with the basidia on the gills of 

 agarics is to fertilise tJie spores, and that to secure cross- 

 fertilisation insect agencv is necessary. This theory is 

 bv no means established, and in the present state of oiu- 

 knowledge it is impossible to say with any confidence 

 whether the attractive characters of agarics promote dis- 

 persion or fertilisation or even to be sure that they 

 arc serviceable in any way. 



The conditions under which plants live are not indeed 

 such that the same amount of protection is required as 

 in the case of animals, and it is hardly to be expected 

 that their imitative powers should equal those of the 

 animal world either in the extent to which deception is 

 carried or in the variety of disguises assumed. The facts 

 we have considered are sufficient, however, to show that 

 in the two kingdoms of organic nature we have to deal 

 with essentially the same phenomena. 



The advocates of natural selection have constantly 

 appealed with the utmost confidence to the evidence 

 from mimicry in support of the theory, but this line of 

 proof is by no means so convincing as has been supposed. 

 No doubt the green colour of caterpillars may be easily 

 accounted for by the extermination of the individuals 

 which happened to be otherwise attired. Many facts, 

 however, indicate that the explanation is not quite so 

 simple ; this line of reasoning would certainly lead us 

 into error in the case of the ilat fishes. When a flounder 

 IS transferred from a tank with sand to one with a 

 gravelly bottom spots at once appear on the fish har- 

 monizing with the gravel, due apparently to reflex action 

 arising from an alteration in the light rays. Nature 

 even seems to possess the secret of photographing in 

 colours, for the pupae of several butterflies acquire the 

 colour of the box in which they are kept. Accordingly 

 Mr. A. R. Wallace, while attributing true mimicry as 

 we have it in the butterfly Leptalis to natural selection, 

 is constrained to refer the general similarity of tint to 

 their surroundings which so many animals exhibit, to 

 the action of light rays reflected from the environment. 

 Our recently acquired knowledge of the Rontgen rays 

 and their effects is not without a bearing on the question 

 at issue. Many substances are known to emit invisible 

 rays capable of giving rise to changes in the molecular 

 arrangement of organic bodies. There can be little doubt 

 therefore that the influence of radiant matt<>r on the 

 highly complex and plastic substances df living bodies 

 has played an important part in bringing about those 

 remarkable resemblances which are included under the 

 terms mimicry and homomorphism. Such considerations 

 •do, however, detract very seriously from the value of 



natural selection as a factor in organic evolution; so far 

 as mimicry is concerned there is little left for natural 

 selection to do, only the finishing touches, so to speak. 



The phenomena of homomorphism are also to some 

 extent adverse to the IJai-winian theory. If we assume 

 with Darwin that variation is fortuitous the law of 

 probabilities forbids us to expect coincidences like that 

 observed in the orchids and asclcpias. In dealing out 

 cards, for example, the chances against a player receiving 

 the same set a second time arc very great, and the im- 

 j)robability increases in a geometrical ratio as the number 

 of cards is increased ; with a large number of cards the 

 improbability is infinitely great. There is the same kind 

 of improbability and that in a high degree against the 

 production through fortuitous variation and natural 

 selection of those coincidences which are so frequent in 

 the organic world. Danvin felt the force of this ob- 

 jection, which he met by saying — " As two men have 

 sometimes independently hit upon the same invention, 

 so it appears that natural selection working for the good 

 of each being and taking advanta,ge of all favourable 

 variations has produced similar organs, as far as function 

 is concerned in distinct organic beings which owe none 

 of their stnictiire in common to inheritance from a com- 

 mon progenitor." But this reply does not quite dispose 

 of the difficulty; the two cases are not strictly 

 analogous; to make them parallel we should have to 

 .sup])ose that two men accidentally and quite uninten- 

 tionally alighted iipon the same invention — a rare 

 occui-rence indeed. Yet such a supposition is necessary 

 ill order to eliminate the element of intelligent investi- 

 gation on the part of the two inventors, to which there 

 is nothing corresponding in natural selection. When two 

 similar vai-iations have arisen natural selection 

 sufficiently accounts for their preservation ; tlic difficulty 

 is the appearance at two or more points of the orLraiiic 

 system of identical variations. That this has occurred 

 again and again goes to show, either that the environ- 

 ment has exercised a definite influence in generating 

 particular variations, or that there is in organisms an 

 innate t^endency to vary along certain lines. In any 

 case variation cannot be fortuitous, but must have its 

 course dominated by fixed, though it may be unascer- 

 tained laws. There is profound biological truth in 

 Emerson's words : ' Natirre's dice are always loaded." 



But a still wider question confronts us. If resem- 

 blances can arise among organisms apart, altogether from 

 hereditary relationship what, it may be asked, becomes 

 of the argument for organic evolution based on similarity 

 of structure ? If, as Darwin admitted, the eye of a cuttle- 

 fish and the eye of a vertebrate had an independent 

 origin, may not the same thing hold good in regard to 

 many of those likenesses to which evolutionists appeal in 

 support of their theory ? Homomorphic is differentiated 

 from hereditary resemblance by the absence of connects 

 ing forms. The evolutionist postulates the former 

 existence of innumerable intermediate forms. If these 

 never had any existence then the alternatives are either 

 evolution per salfum or independence of origin. Between 

 the inorganic and the animate no intermediate forms 

 are conceivable; we are therefore compelled to assume 

 an independent origin for life. jVnd although we cannot 

 form a definite conception of such an occurrence, few 

 naturalists nowadays will be satisfied with a single 

 primitive type as the original source of all the manifold 

 forms of life. But whatever view wp may hold on this 

 point, it is impossible to conceive of the succe.ssive ad- 

 vances in the organization of plants and animals which 

 have taken place in past geological time apart from 

 corresponding accessions of vital energy. 



