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SCIENCE-GOSSIP. 



EVOLUTION BY DISCONTINUOUS VARIATION. 



By G. W. Bulman, M.A., B.Sc. 



"|\ /TR. Bateson is one of the many evolutionists 

 who, having weighed the theory of natural 

 selection as propounded by Darwin and found it 

 wanting, have proposed various amendments and 

 improvements. Like others who have felt the 

 difficulties of natural selection, Mr. Bateson has 

 preferred to try and put a patch on the old view 

 rather than discard it, or propose one entirely new. 

 The reason of this probably is that, in the present 

 temper of biological science, only those who retain 

 at least the old name can hope for a hearing. In 

 effect, each one seems to say, as he removes this or 

 that supporting pillar of the Darwinian scheme : 

 " We have taken away this support, but we have 

 inserted in its place a very strong prop. The 

 building stands as firmly as ever." The patched 

 garment, they profess, is quite as good as the 

 original. 



The peculiar difficulties felt by Mr. Bateson may 

 be expressed briefly as follows. Species as we see 

 them in nature are discontinuous, that is there 

 is an absence of graduated series of connect- 

 ing links between them. Now, says Mr. Bateson, 

 the surrounding conditions to which these species 

 have adapted themselves are continuous, therefore, 

 according to the theory of natural selection, the 

 species should be continuous also. Again, the old 

 familiar difficulty so often urged and so often 

 replied to— the difficulty of conceiving how any 

 character in the initial state of some minute varia- 

 tion can be of any advantage in the struggle for 

 life and so be preserved, is once more brought into 

 prominence. In these again, like other objectors 

 in their special objections, our author carries us 

 with him. It is ground we have already gone over 

 for ourselves. 



Referring to the usual methods of investigating 

 biological problems on the theory of descent, 

 Mr. Bateson is emphatic as to their unsoundness : 

 " In these discussions we are continually stopped 

 by such phrases as, ' If such and such a variation 

 took place and was favourable ' ; or, ' We may easily 

 suppose circumstances in which such a variation, 

 if it occurred, might be beneficial,' and the like. 

 The whole argument is based on such assumptions 

 as these, assumptions which, were they found in 

 the arguments of Paley or of Butler we could not 

 too scornfully ridicule." No one who has studied 

 the literature of evolution with an unprejudiced 

 mind, and is familiar with the genealogical tree, 

 and accounts of how various particular animals 

 have been evolved, will think that this is putting 

 it too strongly. 



The difficulty felt by Mr. Bateson, of discontinuity 

 of species in spite of continuity of environment, 

 and supposed derivation from continuous variation, 

 is more familiar to us under the title of absence of 

 connecting links. We have all heard frequently 

 the ingenious explanations put forward to meet this 

 difficulty. But we agree with Mr. Bateson's con- 

 tention, that though " explained," this difficulty 

 has not been met. Possibly those who have 

 explained it have convinced themselves — though 

 this is perhaps doubtful, for the elasticity of the 

 scientific conscience is great, and the scientific 

 digestion for crude theory is as that of the ostrich — 

 but they have convinced no impartial critic. 



The same difficulty occurs in equal force with 

 regard to the past ; the numerous intermediate 

 gradations required by the theory are wanting 

 in the geological record. It will, however, be 

 urged : has not Darwin explained this by showing 

 the imperfection of this record ? Darwin certainly 

 has shown that the record is extremely imperfect, 

 and most geologists agree with him ; but is this 

 enough ? Can the record be imperfect only in one 

 way ? Or will any sort of imperfection explain the 

 absence of continuity ? We think a similar mis- 

 take has been made here as in the Darwinian 

 explanation of the struggle for existence. Thus 

 the severity of the struggle, the percentage killed 

 off, is dwelt upon as if that were sufficient, irrespec- 

 tive of the nature of the same, to preserve slight 

 favourable variations. Yet, as the struggle might 

 be ten-fold more severe than it has been shown to 

 be, and yet have no tendency to preserve slight 

 differences, so the geological record might be 

 equally more imperfect than even Darwin has 

 proved it, and yet give clear evidence of continuous 

 evolution if such had taken place. What, then, is 

 the nature of the imperfection of the geological 

 record ? In an incomplete historical record there 

 might be a continuous and minute narrative of a 

 particular period or course of events, with blanks 

 or gaps relating to others. We do not expect in a 

 mutilated written record to find every alternate 

 page torn out, or ever)' alternate line obliterated. 

 Yet this is something like what Darwin demanded 

 in the geological record : only such an assumption 

 prevents the facts from clashing with his views. 



Why should the record be imperfect in this 

 way ? Studying the nature of the geological 

 process by which the record is written we should 

 rather expect to find it continuous in certain 

 places, with great gaps in" others. Thus a river 

 carrying down its sediments to the sea along with 



