March 17, 192 1] 



NATURE 



89 



The Inheritance of Acquired Characters. 



FOR a generation it has been a cardinal principle 

 of thought and teaching with a majority of 

 biologists that acquired characters are not inherited. ' 

 Under the influence of Weismann and his doctrine 

 of the independence of germ and soma this position 

 has frequently been adopted even in its extreme 

 form, that the inheritance of acquired characters is 

 an impossibility. Botanists, on the other hand, have 

 usually been less dogmatic on the subject, probably 

 because in higher plants there is no such early segre- 

 gation of germ-cells and somatic cells as occurs in 

 many animals. j 



But in recent years new experiments have exhibited ; 

 the problem in fresh lights, and the tendency to | 

 dogmatism which had grown up around the subject is 

 fast disappearing. Prof. E. VV. MacBride, in a 

 trenchant article {Science Progress, January) which 

 will mark a new stage in the discussion of this 

 problem, subjects various aspects oi Weismannism to 

 a searching criticism, and shows how arguments 

 which seemed so triumphantly unanswerable in Weis- 

 mann 's time are no longer in accord with the modern i 

 facts of experimental biology. i 



Perhaps the most fundamental of the defects of l 

 Weismannism as a philosophy of the organism was 

 its foundation upon purely morphological conceptions 

 of heredity, variation, and organic structure. While we 

 shall always be indebted to him for the emphasis 

 which he laid upon the chromosomes as a basis of ' 

 heredity, yet a considerable part of the superstructure 

 which he built on that foundation is no longer in 

 accord with modern experiment. As Prof. MacBride 

 points out, Weismann 's view that the differentiation 

 during ontogeny is the result of differential divisions 

 of the chromosomes in mitosis is contrary to the 

 evidence of both experimental embryology and cyto- 

 logy. Rather, the conclusion seems clear that all 

 the nuclei of an organism are equipotential, the split- 

 ting of the chromosomes being, as it appears under 

 the microscope, an equal one. If that is the case, 

 then the nuclei may be looked upon as the conserva- 

 tive repositories of many at least of the differences 

 which arise between spjecies, while the mass divi- 

 sions of the cytoplasm account for the greater part 

 of the differentiation which takes place during 

 development. 



Another weakness in Weismannism which Prof. 

 MacBride points out is the assum)3tion that although : 

 the germ-cells of an organism might be affected by 

 climate, they could not be modified by the fluids I 

 from the body-tissues in which they were immersed. \ 

 The physiologists, by means of hormones, enzymes, 

 antibodies, cytolysins, etc., have helped to rescue us 

 from the untenable position that the germ-cells are 

 completely insulated within the organism, and the 

 work of various investigators has led us to see 

 that germinal changes can be experimentally pro- 

 duced. 



This does not, however, necessarily involve the 

 principle of the inheritance of acquired characters, 

 but it does render it reasonable to suppose that such 

 inheritance may take place. The question then 

 reduces itself to one of unprejudiced evidence, and on 

 this point Prof. MacBride refers to the much-discussed 

 investigations of Kammerer, whose results can now 

 be contradicted only by imputing fraud, and to the 

 perhaps even more important, because incontrovertible, 

 evidence recently obtained by Messrs. Guyer and 

 Smith (see article by Prof. Dendy in Nature for 

 February 3, p. 742) in producing a race of rabbits 

 with defective eyes by the action of a cytolysin on 

 the mother. 



It is clear that the Lamarckian principle of use 

 and disuse, as well as the various Neo- Lamarckian 

 subtleties involving the inheritance of acquired charac- 

 ters, will have to be reckoned with seriously in future 

 as an evolutionary factor. There is one point, how- 

 ever, in which we would venture to differ from Prof. 

 MacBride, and that is with regard to the evolutionary 

 significance to be attached to mutations. It is true 

 that many of the mutations studied in plants and 

 animals are more or less pathological or abnormal, 

 and would stand a very poor chance of surviving in 

 equal competition under wild conditions. On the 

 theory of mutations this is to be expected, as well as 

 the occurrence of many lethal factors such as are 

 now known in Drosophila and CEnothera. But viable 

 mutations, or even those which in some circumstances 

 will have an advantage over the parent species, are 

 by no means unknown. Bridges {Biol. Bull., 

 vol. xxxviii., p. 231) has recently described a mutation 

 in Drosophila with white ocelli, which maintained 

 itself in equal numbers in competition with the type 

 in mass-culture for about 175 generations. The 

 character-difference is here insignificant, but in wild 

 species of plants there are innumerable records of 

 single variations which have arisen and perpetuated 

 themselves, having neither an advantage nor a dis- 

 advantage in competition with the parent species so 

 far as can be determined. 



Mutations are also by no means all loss characters. 

 In the CEnotheras a series of forms is now known 

 having a whole extra chromosome in their nuclei ; 

 and since the doubling of the whole series of chromo- 

 somes (tetraploidy) was investigated in CEnothera 

 gigas, a large number of genera of nlants have been 

 found to contain tetraploid species, showing that this 

 particular type of mutation is not only in a sense 

 progressive, but has also taken part in the phylogeny 

 of various genera and families. 



May we not, then, suppose that mutation and the 

 Lamarckian factor have both played their part in 

 evolution, natural selection frequently coming in to 

 adjudicate between mutations, while the Lamarckian 

 factor has been at work in many cases of adaptation ? 



R. RuGGLES Gates. 



Home-grown Wheat. 



T^HE Ministry of .Agriculture has instituted a cam- 

 ■'• paign to secure by educational methods an 

 increase in the wheat production of this country. An 

 account of the addresses delivered in connection with 

 this campaign by the principal of the Harper-Adams 

 Agricultural College appeared in the Ministry's 

 General Service for December 11 last. These ad- 

 dresses dealt with the subject from two points of 



NO. 2681, VOL. 107] 



view : the need for stimulating production and the 

 I best methods of raising the average yield. 



Though Great Britain obtains its wheat from many 

 I parts of the world, and it is scarcely conceivable that 

 I a shortage would occur through simultaneous failure 

 ' of the crops in all these countries, yet it is imperative 

 : that our own yield should be increased, since the 



available figures from other producing countries and 



