330 



NA TURE 



[August 2, 1906 



of observations and writings of August Weismann, who has, 

 in the opinion of the majority of those who study this 

 subject, rendered the I.amarckian theory of the origin and 

 transmission of new characters altogether untenable, and 

 has, besides, furnished a most instructive, if not finally 

 conclusive, theory or mechanical scheme of the phenomena 

 of Heredity in his book "The Germ-plasm." Prof. Karl 

 Pearson and the late Prof. Weldon — the latter so early 

 in life and so recently lost to us — have, with the finest 

 courage and enthusiasm in the face of an enormous and 

 diflicult task, determined to bring the facts of variation and 

 heredity into the solid form of statistical statement, and 

 have organised, and largely advanced in, this branch of in- 

 vestigation, which they have termed " Biometrics." Many 

 naturalists throughout the world have made it the main 

 object of their collecting and breeding of insects, birds, and 

 plants, to test Darwin's generalisations and to expand 

 the work of Wallace in the same direction. A delightful 

 fact in this survey is that we find Mr. Alfred Russel Wallace 

 (who fifty years ago conceived the same theory as that more 

 fully stated by Darwin) actively working and publishing 

 some of the most convincing and valuable works on 

 Darwinism. He is still alive and not merely well, but 

 pursuing his work with vigour and ability. It was chiefly 

 ihrough his researches on insects in South America and the 

 Malay Islands that Mr. Wallace was led to the Darwinian 

 theory ; and there is no doubt that the study of insects, 

 especially of butterflies, is still one of the most prolific 

 fields in which new facts can be gathered in support of 

 Darwin and new views on the subject tested. Prominent 

 amongst naturalists in this line of research has been and 

 is Edward Poulton of Oxford, who has handed on to the 

 study of entomology throughout the world the impetus of 

 the Darwinian theory. I must here also name a writer 

 who, though unknown in our laboratories and museums, 

 seems to me to have rendered very valuable service in later 

 years to the testing of Darwin's doctrines and to the bring- 

 mg of a great class of organic phenomena within the 

 cognisance of those naturalists who are especially occupied 

 with the problems of Variation and Heredity. I mean 

 Dr. Archdall Reid, who has with keen logic made use of 

 the immense accumulation of material which is in the 

 hands of medical men, and has pointed out the urgent 

 miportance of increased use by Darwinian investiga'tors 

 of the facts as to the variation and heredity of that unique 

 animal, man, unique in his abundance, his reproductive 

 activity, and his power of assisting his investigator by 

 his own record. There are more observations about the 

 variation and heredity of man and the conditions attend- 

 ant upon individual instances than with regard to any other 

 animal. Medical men need only to grasp clearly the ques- 

 tions at present under discussion in order to 'be able to 

 furnish with ease data absolutelv invaluable in quantity 

 and quality. Dr. Archdall Reid has in two original books 

 full of insight and new suggestions, the " Present Evolution 

 of Man " and " Principles of Heredity," shown a new path 

 for investigators to follow. 



The attempt to resuscitate Lamarck's views on the in- 

 heritance of acquired' characters has been met not only by 

 the demand for the production of experimental proof that 

 such inheritance takes place, which has never been pro- 

 duced, but on Weismann 's part by a demonstration that 

 the reproductive cells of organisms are developed and set 

 aside from the rest of the tissues at so earlv a period that 

 it is extremely improbable that changes brought about in 

 those other tissues by unaccustomed incident forces can 

 be communicated to the germ-cells so as to make their 

 appearance in the ofi'spring by heredity. Apart from this, 

 I have drawn attention to the fact that' Lamarck's first and 

 second laws fas he terms them) of heredity are contra- 

 dictory the. one of the other, and therefore may be dis- 

 missed. In iSq4 I wrote : 



" Normal conditions of environment have for many 

 thousands of generations moulded the individuals of a 

 given species of organism, and determined as each in- 

 dividual developed and grew ' responsive ' quantities in its 

 parts (characters) ; yet, as Lamarck tells us, and as we 

 know, there is in every individual born a potentiality which 



1 I use the term " acquired " without prejudice in the sense given to 

 that word by Lamarck himself. 



NO. I 9 18, VOL 74] 



has not been extinguished. Change the normal conditions 

 of the species in the case of a young individual taken to- 

 day from the site where for thousands of generations its 

 ancestors have responded in a perfectly defined way to the 

 normal and defined conditions of environment ; reduce the 

 daily or the seasonal amount of solar radiation to which 

 the individual is exposed ; or remove the aqueous vapoui 

 from the atmosphere ; or alter the chemical composition of 

 the pabulum accessible ; or force the individual to previously 

 unaccustomed muscular effort or to new pressures and 

 strains ; and (as Lamarck bids us observe), in spite of all 

 the long-continued response to the earlier normal specific 

 conditions, the innate congenital potentiality shows itself. 

 The individual under the new quantities of environing 

 agencies shows new responsive quantities in those parts of 

 its structure concerned, new or acquired characters. 



" So far, so good. What Lamarck next asks us to 

 accept, as his ' second law,' seems not only to lack the 

 support of experimental proof, but to be inconsistent with 

 what has just preceded it. The new character which is 

 ex hypothesi, as was the old character (length, breadth, 

 weight of a part) which it has replaced — a response to 

 environment, a particular moulding or manipulation by 

 incident forces of the potential congenital quality of the 

 race — is, according to Lamarck, all of a sudden raised to 

 extraordinary powers. The new or freshly acquired 

 character is declared by Lamarck and his adherents to be 

 capable of transmission by generation ; that is to say, it 

 alters the potential character of the species. It is no 

 longer a merely responsive or reactive character, deter- 

 mined quantitatively by quantitative conditions of the 

 environment, but becomes fi.xed and incorporated in the 

 potential of the race, so as to persist when other quanti- 

 tative external conditions are substituted for those which 

 originally determined it. In opposition to Lamarck, one 

 must urge, in the first place, that this thing has never been 

 shown experimentally to occur ; and in the second place, 

 that there is no ground for holding its occurrence to be 

 probable, but, on the contrary, strong reason for holding 

 it to be improbable. Since the old character (length, 

 breadth, weight) had not become fixed and congenital after 

 many thousands of successive generations of individuals 

 had developed it in response to environment, but gave place 

 to a new character when new conditions operated on an 

 individual (Lamarck's first law), why should we suppose 

 that the new character is likely to become fixed after a 

 much shorter time of responsive existence, or to escape 

 the operation of the first law? Clearly there is no reason 

 (so far as Lamarck's statement goes) for any such sup- 

 position, and the two so-called laws of Lamarck are at 

 variance with one another." 



In its most condensed form my argument has been 

 stated thus by Prof. Poulton : Lamarck's " first law 

 assumes that a past history of indefinite duration is power- 

 less to create a bias by which the present can be con- 

 trolled ; while the second assumes that the brief history 

 of the present can readily raise a bias to control the 

 future " (Nature, vol. li., 1894, p. 127). 



An important light is thrown on some facts which seem 

 at first sight to favour the Lamarckian hypothesis by the 

 consideration that, though an " acquired " character is 

 not transmitted to offspring as the consequence of the 

 action of external agencies determining the " acquirement," 

 yet the tendency to react exhibited by the parent is trans- 

 mitted, and if the tendency is exceptionally great a false 

 suggestion of a Lamarckian inheritance can readily result. 

 This inheritance of " variation in tendencies to react " 

 has a wide application, and has led me to coin the word 

 " educability " as mentioned in the section of this address 

 on Psychology. 



The principle of physiological selection advocated by Dr. 

 Romanes does not seem to have caused much discussion, 

 and has been unduly neglected by subsequent writers. It 

 was ingenious, and was based on some interesting observ- 

 ations, but has failed to gain support. 



The observations of de Vries — showing that in cultivated 

 varieties of plants a new form will sometimes assert itself 

 suddenly and attain a certain period of dominance, though 

 not having been gradually brought into existence by a slow 

 process of selection — have been considered by him, and by 



