REVIEWS. 



Menders Principles of Heredity.-^ w. Bateson, m.a., 



F.R.S., V.M.H., Fellow of St. John's College, Professor of 

 Biology in the University of Cambridge. Cambridge, at the 

 University Press. 1909. 



Professor Bateson's book will remain as the classic exposition 

 of Mendelism. No man more than he has served by the brilliance 

 and patience of his work, and the insight indicated by his methods, 

 to place Genetics, or the study of Heredity, upon what is in reahty 

 its first enduring foundation. Whatever may be the ampUfica- 

 tions and extensions which future investigation may necessitate, 

 we do not think there is much doubt that the basis of the Science 

 of Inheritance, which is now being reared by the MendeUan 

 School, will remain as a permanent edifice in biological science. 

 The conceptions of gametic segregation and gametic purity have 

 come to stay. That the processes embraced within these con- 

 ceptions play a part in inheritance and in evolution is clear 

 enough. Whether they are the sole agencies at work, or whether 

 their pari; in Nature, though limited, is of wide extent, is a 

 question for the future to answer. But no conception of Nature 

 Avhich omits them can be complete, or have any pretence to be 

 regarded as full or sound. 



If inheritance and evolution are wholly or in part based upon 

 gametic segregation, then our conceptions of the essential nature of 

 the phenomena of variation will benecessarily profoundly modified. 

 For, as is pointed out in the article in this Journal on " Mendel's 

 Life and Work," it is difficult to picture the process of evolution 

 as merely a matter of the blending of minute incremental varia- 

 tions all tending in one direction, while the processes going on in 

 the sex-cells are those of segregation. We may as well try to 

 imagine that St. Paul's Cathedral was reared by a continuous 

 welling upward motion of Uquid stufi, while all the time we know 

 that it was built up of solid, separate blocks, deftly laid and 

 arranged, one by one. It was not constructed by a flowing pro- 

 cess, but by the sequential addition of separate though small 

 steps, each block and brick of its masonry representing a step 

 Tipward. 



Thus we have before us these two conceptions of evolu- 

 tion as a process based on variation. It is clear, to start 



