242 



SCIENCE 



[N. S. Vol. XL. No. 1024 



The Silliman lectures delivered at Yale 

 by Professor Bateson in 1907, revised and 

 published in 1913 under; the title " Problems 

 of Genetics," form one of the most stimula- 

 ting and suggestive books for students of Evo- 

 lution and Heredity ■which has appeared since 

 the rediscovery of Mendel's law. Like other 

 books by the same author, it is not designed 

 for beginners but for actual workers in the 

 field covered, and is no fit food for babes and 

 sucklings. To the student familiar with cur- 

 rent theories and lines of investigation con- 

 cerning evolution the frank criticism of those 

 theories and investigations will be especially 

 valuable. Present knowledge is recognized to 

 be imperfect and tentative, and while the au- 

 thor expresses an emphatic preference for cer- 

 tain views, he holds them without dogmatism 

 or claim to finality, an attitude in scientific 

 work which, with every advance, we need to 

 remind ourselves of anew. 



In his introduction, Bateson addresses him- 

 self to the old but unsolved question of the 

 nature and origin of species, which he blames 

 the discussion over natural selection for ob- 

 scuring. He says : " In the enthusiasm with 

 which evolutionary ideas were received the 

 specificity of living things was almost for- 

 gotten. The exactitude with which the mem- 

 bers of a species so often conform in the diag- 

 nostic, specific features passed out of account; 

 and the scientific world by dwelling with a 

 constant emphasis on the fact of variability, 

 persuaded itself readily that species had after 

 all been a mere figment of the human mind. 

 Without presuming to declare what future 

 research only can reveal, I anticipate that, 

 when variation has been properly examined 

 and the several kinds of variability have been 

 successfully distinguished according to their 

 respective natures, the result will render the 

 natural definiteness of species increasingly 

 apparent." Bateson rejects natural selection 

 as a sufficient explanation of the origin of 

 species, concluding that we are on safer 

 ground " in regarding the fixity of our species 

 as a property inherent in its own, nature and 

 constitution." He says : " As soon as it is 

 realized how largely the phenomena of varia- 



tion and stability must be an index of the in- 

 ternal constitution of organisms, and not 

 mere consequences of their relations to the 

 outer world, such phenomena acquire a new 

 and more profound significance." In Chap- 

 ters II.-IV., Bateson attempts a classifica- 

 tion of variations along lines indicated in his 

 "Materials" (1896). This may have been 

 important historically in leading Bateson to 

 his later views concerning the discontinuity 

 of evolution, but to most readers will seem 

 aside from the main discussion. Taking up 

 in Chapter V. the mutation theory, he ex- 

 presses the view that a new species originates 

 in a changed " internal constitution of the 

 organism," which with DeVries he believes to 

 arise discontinuously. But the discontinuity, 

 according to Bateson, is of Mendelian unit- 

 characters or factors only. He explicitly re- 

 jects the DeVriesian idea of mutation in- 

 volving a change in a whole group of char- 

 ters simultaneously, and explains the peculiar 

 genetic behavior of (Enothera Lamarckiana 

 as due to hybridization. 



" The facts may, I think, fairly be sum- 

 marized in the statement that species are, on 

 the whole, distinct and not intergrading, and 

 that the distinctions between them are usually 

 such as might be caused by the presence, ab- 

 sence or inter-combination of groups of Men- 

 delian factors; but that they are so caused 

 the evidence is not yet sufficient to prove in 

 more than a: very few instances. 



" The alternative, be it explicitly stated, is 

 not to return to the view formerly so widely 

 held, that the distinctions between species 

 have arisen by the accumulation of minute or 

 insensible difPerences. The further we pro- 

 ceed with our analyses the more inadequate 

 and untenable does that conception of evolu- 

 tionary change become. If the differences be- 

 tween species have not come about by the 

 addition or loss of factors one at a time, then 

 we must suppose that the changes have been 

 effected by even larger steps, and variations, 

 including groups of characters, must be in- 

 voked. 



" That changes of this latter order are 

 really those by which species arise is the view 



