STUDY OF VARIATION 207 



Study of Inheritance," and in one entitled the " Experimental 

 Study of Inheritance." In this latter chapter an account of 

 Mendel's discoveries, of the theoretical interpretations flowing 

 from them, of the recent elaborations of Mendelism and the 

 practical bearing of Mendelian results, are given and discussed. 

 The problem of " Sex " has a chapter to itself, and so also has 

 " Heredity and Development." This last chapter is essentially 

 a statement and discussion of Weismann's theory of the Germ- 

 Plasm. The final chapter deals with " Social Aspects of Bio- 

 logical Results." 



There is appended a Bibliography, a Subject-Index to Biblio- 

 graphy, and an Index. There are forty-nine exceedingly good 

 illustrations and diagrams, and many of them are coloured. 

 They should help to render difficult conceptions clear and easy. 



G.P.M. 



Recent Progress in the Study of Variation, Heredity, 



and Evolution. R. H. Lock, M.A. John Murray, 

 London, o.s. net. Second Edition. Pp. 334. 



The object of Mr. Lock's cleverly written book is to give an 

 account of the modern progress of knowledge relating to heredity, 

 and to attempt to render the account intelligible to the general 

 reader as well as to the more scientific public. In this endeavour 

 Mr. Lock has admirably succeeded. His statement of some of 

 the many questions with which he deals, are the clearest of many 

 that have been written. Some problems are of such a nature 

 that they may be described in a most laborious fashion and 

 rendered more complex than they really are, by the treatment 

 they receive. Professor Johannsen's theory of the " pure lines," 

 is one of this nature. An unskilful pen would render a statement 

 of it intolerably complex and hoijelessly confusing. Mr. Lock's 

 treatment of it recalls our nursery days when we lived in fairy- 

 land, and all our difficulties vanished by the touch of the fairy- 

 queen. We read his description and we grasp its meaning while 

 we do so. And it is the same throughout the book. Indeed^ 

 the criticism we should feel most inclined to make, is that it reads 

 too easily. Readers are apt to imagine that they know more 

 than they really do, if they have gathered that knowledge with 

 too little effort. 



The book gives an account of the evidences of Evolution and 

 of Natural Selection. And, although it is in large measure, a 

 " Mendelian book," the author has written an interesting account 



