NA TURE 



407 



THURSDAY, MAY 25, 191 1. 



MENDELISM AND BIOLOGY. 



Mendel's Principles of Heredity. By W. Bateson, 

 F.R.S. Pp. xiv + 396. (Cambridge: University 

 Press, 1909.) Price 125. net. 



THE time has come when a preliminary attempt 

 may be made to forecast the position which 

 Mendel's discovery will occupy in the history of 

 biolotjv, and when the widely divergent attitudes 

 which have been taken up towards Mendelian prin- 

 ciples may be profitably considered. 



The reviewer is in the present case relieved of the 

 duty, which usually falls to his lot, of indicating the 

 nature, scope, and value of the contents of the book 

 before him; for, whether we agree with Mr. Bate- 

 son or not, sceptics and adherents alike consider that 

 his book is the fullest and most authoritative exposi- 

 tion of the results which have been achieved by those 

 who hnve worked on the lines laid down by Mendel. 

 These results may throw no light on the nature of 

 heredity or on any problem which it has pleased the 

 imagination of biologists to invent ; but, be this as it 

 may, the book before us is the source from which 

 the fullest and most trustworthy information in re- 

 gard to these results is to be sought, and no atten- 

 tion need be paid to the criticisms of those who are 

 not intimate with its contents. Whatever the Men- 

 delian doctrine is, here it is, for better or for worse. 



To estimate the significance of this book we must, 

 therefore, assign this doctrine to a place in the scheme 

 of biology. The degree of success which will attend 

 the efforts of any given person to perform this task 

 will be inversely proportional to the faculty possessed 

 bv him of imagining that he may be mistaken. If 

 he lacks this faculty altogether, complete success, so 

 far as he is concerned, is assured, and the Mendelian 

 hypotheses will either be set down as the correct pic- 

 ture, drawn now finally, once and for all, of the 

 hereditary processes underlying the phenomena which 

 they were invented to explain, or as the fantastic 

 imaginings of unfortunate biologists who are un- 

 willing or unable to take the whole of the available 

 evidence into account. To us, who foster and pre- 

 serve some of the attributes of childhood, these two 

 extreme views appear no more than naive and elemen- 

 tary, the utterances of men who, in the current 

 phrase, "know their own minds." We cannot believe 

 that in every department of the Mendelian hypothesis 

 the explanation offered does more than approximate 

 to that picture of the underlying processes which will 

 ultimately be agreed upon as representing them as 

 accurately as they ever can be represented. Still less 

 can we believe that the Mendelian hypothesis is wide 

 of the mark altogether, and bears no relation at all 

 to the phenomena which it attempts to explain. How 

 iriK .1 representation it is, can only be determined 

 by -^ul;jecting its component hypotheses to rigorous 

 experimental tests. Our own opinion, to which, 

 however, we attach little weight, inasmuch as the 

 experiments designed by us to effect this test are 



xo. 2169, VOL. 86] 



only, as yet, begun, is that the majority of the hypo- 

 theses will stand these tests well. 



We may now pass from the question as to the truth 

 of the Mendelian principles to that of the bearing of 

 these principles on those products of the imagination 

 which we agree to name " great biological problems," 

 such, for instance, as the "nature of hercditv " and 

 the "origin of species." The former question must, 

 we suppose, be regarded as a real one, but, of course, 

 not one any answer to which will ever be regarded 

 as the final one. But the latter involves so many 

 notions, only remotely representing phenomena, and 

 so many generalisations which are manifestly in- 

 terim ones, that the discussion of its relation to 

 Mendelian principles becomes a mere exercise in 

 dialectic offering no prospect of ever so slight a 

 progression in the direction of a clearer vision of 

 actuality. 



Let us deal first with heredity. The problems of 

 heredity which are debated at the present day exist 

 only for those who adopt that view of life which 

 insists on the disparateness and circumscription of the 

 units to the succession of which the continuation of 

 the stream of life is due. To those, on the other 

 hand, who think that the cutting up of this stream 

 into individuals (which, so far as we can see at pre- 

 sent, do certainly appear to be discreet) is an un- 

 warrantable insistence on a secondary feature ; and 

 who think that the difference as regards the living- 

 ness of the objects of their several interests between 

 a man who is not satisfied with observing less than, 

 sav. ten consecutive generations of a living thing 

 and a man who dissects a rabbit, is as great as, and 

 of the same nature as, the difference between a man 

 who dissects a rabbit and a man who collects stamps 

 — to these the favourite problems of heredity do not 

 exist at all, though the material out of which these 

 problems have been constructed is the chief object of 

 their attention. 



With regard to the light thrown by Mendelian re- 

 sults on the question of the origin of species. The 

 idea that the process of specific differentiation is akin 

 to that of Mendelian segregation will doubtless serve 

 as a fertile incentive to investigation for years to come. 

 But to suppose that evolution is due to causes which 

 can be compared to the shuffling of marbles in bags 

 seems to us to be an idea which throws no light on 

 any problem, save on that of the value of the insight 

 of those who are not ashamed to confess that they 

 entertain it. 



The strictly phenomenal or impressionist aspect of 

 specific differentiation must be attacked by means of 

 the instrument which Mendel has put into the hand 

 of biologists— the analysis of the organism into its 

 constituent characters by experimental breeding. But 

 to suppose that the Mendelian method does any more 

 than indicate the lines along which the attack on this 

 particular problem is to be made betrays, in those 

 who make this supped ii.>n, a high degree of that 

 naive sanguineness is to the powers of the 

 human intelligence which constitutes, at the present 

 dav, the most formidable obstacle blocking our ap- 

 proach to a true vision of life and evolution. 



O 



