n^ 



NA TURE 



[June io, 1922 



restricted outlook in the biologist's classification of 

 characters. 



Sir Archdall Reid expostulates with biologists for 

 writing down to the ' nature ' account what should 

 be put to the ' nurture ' account^ but the biologists 

 agree with him in not keeping two accounts. The 

 mistake of making an antithesis between ' nature ' 

 and ' nurture ' — two components of one resultant — 

 is not one to which a biologist can plead guilty. 

 But the biologist understands the difference between 

 hereditary nature realising itself in its normal nurture, 

 and hereditary nature being indented by novel 

 peculiarities. It need not be a ' glaring ' nurtural 

 peculiarity, as Sir Archdall Reid says, — a minimal 

 change, e.g. in salinity, may serve. It must not be 

 supposed, however, that it is easy to distinguish, 

 especially in mammals and seed-plants, between what 

 are antenatal modifications and what are normal 

 expressions of the inheritance. Much is congenital 

 that is not hereditary. If we only knew the wan 

 newt Proteus in the dark waters of the Dalmatian 

 caves, we should surely conclude that the power 

 of producing pigment was not in its inheritance. 

 Yet we should be wrong. The power of producing 

 pigment has not been lost ; it expresses itself whenever 

 the Proteus is exposed to the liberating stimulus of 

 light. Similarly, as to various ' specific characters ' 

 of animals, e.g. parasites, which we know only from one 

 environment, it may be that some of them are purely 

 modificational, like the green of the Colias caterpillars, 

 and imprinted on each successive generation. Further 

 knowledge may show that many characters which we 

 now regard as ' innate ' are only ' imprints ' on an 

 innate susceptibility or receptivity. But our inability 

 to say ' yea ' or ' nay ' in regard to such questions is 

 due to our ignorance, not to any confusion of thought. 



No doubt Sir Archdall Reid has made many true 

 statements, e.g. that, to begin with, the organism and 

 the inheritance are one and the same ; that the in- 

 heritance consists of potentialities or factors, not of 

 characters ; that a specific character is always the 

 product of ' nature ' and ' nurture,' which are com- 

 plementary, not antithetic ; that it is not always easy 

 in practice to distinguish the hereditarily inborn from 

 an antenatal modification ; that functioning often 

 counts for much in development. But with these 

 statements all competent biologists are in agreement. 

 To a large extent Sir Archdall Reid has indulged in 

 bogey-hunting and in the pastime of re-editing the 

 scientific dictionary and then importing fallacies into 

 biological argument. To accuse biologists of not 

 dealing with realities is as absurd as indicating that 

 Lamarck's first law is not sense. When a man pulls 

 his bow so tightly as all that, he hits nothing. 

 NO. 2745, VOL. 109] 



Elements and Isotopes. 



Isotopes. By Dr. F. W. Aston. Pp. viii + 152. 

 (London : E. Arnold and Co., 1922.) 95. net. 



DR. ASTON'S book on " Isotopes " is very far from 

 being a mere reprint of his published papers ; 

 it constitutes a masterly review of all the aspects 

 of the subject with which he deals. As a result, those 

 who are already familiar with the principal papers 

 which have appeared in the Philosophical Magazine 

 will find in the book much that is both interesting and 

 instructive. Thus, the author's account of Dempster's 

 alternative form of the mass-spectograph is particularly 

 interesting ; and Dr. Aston has rendered a real service 

 to readers who are not specialists by bringing together 

 in one volume all the methods and results of work on 

 isotopes. His summary of the investigations which 

 have been carried out on radioactive isotopes is 

 particularly concise and readable. 



The discovery of isotopes, and particularly of isotopes 

 which are not radioactive, has brought into prominence 

 the necessity for considering afresh the definition of 

 an element. In practice two methods have been 

 adopted. In the radioactive series each isotope has 

 been regarded as a separate element, and has been 

 given a separate name and a separate symbol ; this 

 practice has arisen naturally in view of the fact that 

 the isotopes, although having the same atomic number, 

 differ not only in their atomic weight, but also in the 

 source from which they are prepared, and in their 

 stability as measured for instance by the half-life 

 period. On the other hand, it is equally in accordance 

 with traditional methods that chlorine, which has 

 been described as an element ever since the appearance 

 of Davy's celebrated Memoir in 1810, should still be 

 treated as an element in spite of the fact that it is 

 now known to contain two isotopes, the atoms of 

 which differ from one another by two units of atomic 

 weight. This alternative view is supported by Dr. 

 Aston, who recommends that all atoms having the same 

 atomic number should be regarded as isotopes of one 

 element, the number of elements being thus limited 

 to 92. Having regard to the fact that inactive isotopes 

 (with the exception of lead) occur in nature in constant 

 proportions, and that the alteration of these propor- 

 tions is a matter of very great difficulty, it is unlikely 

 that any complications would arise amongst practical 

 chemists if chlorine and bromine were still to be 

 described as elements instead of as mixtures of elements. 

 It is, however, clear that the two alternative usages 

 which have been described above cannot both persist, 

 and that we must either adopt some common symbol 

 and name for each group of radioactive isotopes, e.g. 

 for the three radioactive emanations, or adopt some 



