90 Heredity and Variation in Modern Lights 



and disuse" would be a materially different book. A certain vacillation 

 is discernible in Darwin's utterances on this question, and the fact 

 gave to the astute Butler an opportunity for his most telling attack. 

 The discussion which best illustrates the genetic views of the period 

 arose in regard to the production of the rudimentary condition of the 

 wings of many beetles in the Madeira group of islands, and by com- 

 paring passages from the Origin 1 Butler convicts Darwin of saying 

 first that this condition was in the main the result of Selection, with 

 disuse aiding, and in another place that the main cause of degenera- 

 tion was disuse, but that Selection had aided. To Darwin however 

 I think the point would have seemed one of dialectics merely. To 

 him the one paramount purpose was to show that somehow an 

 Evolution by means of Variation and Heredity might have brought 

 about the facts observed, and whether they had come to pass in the 

 one way or the other was a matter of subordinate concern. 



To us moderns the question at issue has a diminished significance. 

 For over all such debates a change has been brought by Weismann's 

 challenge for evidence that use and disuse have any transmitted 

 effects at all. Hitherto the transmission of many acquired charac- 

 teristics had seemed to most naturalists so obvious as not to call for 

 demonstration 2 . Weismann's demand for facts in support of the 

 main proposition revealed at once that none having real cogency 

 could be produced. The time-honoured examples were easily shown 

 to be capable of different explanations. A few certainly remain 

 which cannot be so summarily dismissed, but — though it is manifestly 

 impossible here to do justice to such a subject — I think no one will 

 dispute that these residual and doubtful phenomena, whatever be 

 their true nature, are not of a kind to help us much in the inter- 

 pretation of any of those complex cases of adaptation which on the 

 hypothesis of unguided Natural Selection are especially difficult to 

 understand. Use and disuse were invoked expressly to help us over 

 these hard places ; but whatever changes can be induced in offspring 

 by direct treatment of the parents, they are not of a kind to en- 

 courage hope of real assistance from that quarter. It is not to be 

 denied that through the collapse of this second line of argument the 

 Selection hypothesis has had to take an increased and perilous 

 burden. Various ways of meeting the difficulty have been proposed, 



1 6th edit. pp. 109 and 401. See Butler, Essays on Life, Art, and Science, p. 265, 

 reprinted 1908, and Evolution, Old and New, chap. xxn. (2nd edit.), 1882. 



2 W. Lawrence was one of the few who consistently maintained the contrary opinion. 

 Prichard, who previously had expressed himself in the same sense, does not, I believe, 

 repeat these views in his later writings, and there are signs that he came to believe in the 

 transmission of acquired habits. See Lawrence, Lect. Physiol. 1823, pp. 436 — 437, 447 

 Prichard, Edin. Inaug. Disp. 1808 [not seen by me], quoted ibid, and Nat. Hist. Man, 

 1843, pp. 34 f. 



