202 



NATURE 



[May 15, 1919 



related evolution of a multitude of characters in 

 one organism (which is aptly likened to an ad- 

 vancing- army with units, companies, and regi- 

 ments) ; (e) the importance of what we venture 

 to call temporal variations — i.e. plus and minus 

 changes in the rate or tempo of the evolution of 

 various parts of the body, which may perhaps be 

 correlated with variations in glands of internal 

 secretion; (/) the insistence on the palaeonto- 

 logical evidence, which has accumulated since 

 Waagen's day, thanks in great part to Prof. 

 Osborn's own industry, that the evolution of 

 characters often proceeds by minute and definite 

 changes ; and [g] what we confess to having an in- 

 corrigible pleasure in welcoming, an admission that 

 the "initiative" of the organism counts. Prof. 

 Osborn's concept of "interaction" does not seem 

 to us to differ from the concept of "correlation" 

 or "integration" with which many of us have 

 worked, but perhaps he has done more justice to 

 it than have others. At any rate, his clear view 

 of the dynamical aspect of the organism has 

 resulted in an uncommonly fresh and stimulating 

 book which will make many students of biology 

 grateful. We wish we had space for more than 

 a word of praise for the abundant illustrations, 

 which are very original and telling. 



J A. T. 



EXPERIMENTS IN BIOLOGICAL METHOD. 

 (i) The Quantitative Method in Biology. By 

 Prof. Julius MacLeod. ("Publications of the 

 University of Manchester," Biological Series, 

 No. II.) Pp. xii + 228. (Manchester: Uni- 

 versity Press ; London : Longmans, Green, and 

 Co., 1919.) Price 155. net. 

 (2) A Text-hook of Biology. For Students in 

 General, Medical, and Technical Courses. By 

 Prof. William Martin Smallwood. Third 

 edition, enlarged and thoroughly revised. 

 Pp. 306. (Philadelphia and New York : Lea 

 and Febiger, 1918.) Price 105. 6d. net. 

 A , T intervals, in every science, investigators 

 •^^ and teachers begin to become dissatisfied 

 with accepted methods. They come to realise 

 that the methods in vogue were adapted to a 

 certain stage in the devdopment of the science, 

 and that as the science progresses changes both 

 In the means of investigation and in the manner 

 of teaching become needful. The two books 

 under review have one feature, and perhaps only 

 one, in common ; they both are attempts to Intro- 

 duce improved methods, the one in investigation, 

 the other in teaching. 



(i) Prof. MacLeod, of Ghent, while resident at 

 Manchester, has continued his studies on what 

 might be called biometry were not his methods 

 so different from those of the English school of 

 biometricians, and expounds his aims for the 

 benefit of British readers. He tells us that in the 

 physical sciences "the properties of objects are 

 measured and expressed by means of figures 

 called constants," while in biology "the proper- 

 NO. 2585, VOL. 103] 



ties (characters) of the. living things are usually 

 described by means of terms " (long, shorty 

 narrow, oval, etc.). "The object of the present, 

 book is to describe a method by which biological 

 constants may be established." He begins by 

 assuming that there is a chemical basis forsp€cies> 

 for the living basis of each species is a mixture 

 of chemical substances, and these specific mix- 

 tures differ from one another by at least one 

 entity. Species are thus essentially discontinu- 

 ous, but every specific property is the resultant 

 of a reaction between the specific mixture and 

 environmental forces. Hence arises plasticity- — ■ 

 the variation of species due to environmental 

 differences. Variation due to plasticity and 

 that due to germinal change can be investigated 

 adequately only by quantitative methods, as is 

 recognised by both the biometric and Men- 

 delian schools. But exact methods are needed^ 

 especially in systematic biology, and also in em- 

 bryology, comparative anatomy, and physiology, 

 and it is suggested that many new facts and ideas, 

 would come to light if this were more generally 

 recognised. For this purpose the author seeks 

 in each species investigated a number of simple 

 properties, analogous with Mendelian unit char- 

 acters, which can be observed and recorded accu- 

 rately. These he calls primordia, and they are- 

 such that each is the expression of a state of 

 equilibrium at the time when it is observed, 

 though it may disappear or change to a different 

 primordium later. For example, the petals of the 

 forget-me-not are first white, then pink, then 

 blue ; white and pink are transitory primordia, 

 blue is persistent. Most primordia chosen are 

 measurable — lengths, numbers of segments, and 

 so forth — but such features as colour or texture 

 may also be used. 



By means of the study of such primordia, 

 made by the author chiefly in plants and insects^ 

 a number of principles are deduced, with which 

 all biologists are familiar in an Indefinite sense,, 

 but which are rarely expressed in a concrete form. 

 Of these may be mentioned especially gradation, 

 defined as the variation of a given property along 

 a given axis (as, for example, the lengths of suc- 

 cessive internodes in plants), and also a number 

 of curious and ingenious comparisons between 

 organic variation and the numerical results of 

 chance in regard to the tossing of coins, throwing- 

 of dice, etc. 



The main aim of the book, however, Is to show- 

 that by making sufficient measurements of inde- 

 pendently varying "primordia" true biological 

 constants are obtained. For if a sufficient number 

 of specimens are examined (and the author shows 

 that this number need not be excessively large), 

 the maximal, and sometimes also the minimal, 

 value of each primordium is " a strictly determined" 

 biological constant," so that a collection of such 

 constants Is not only an adequate and easily used 

 diagnosis of the species, but may be used also 

 for the study of development, comparative 

 anatomy, and the Influence of environment (plas- 

 ticity). Though the book contains much that is 



