BOOK REVIEWS. 



81 



be present and from half it will be absent. This last phenomenon, 

 which is called segregation, constitutes the essence of Mendel's dis- 

 covery." 



Professor Bateson modestly shows, in passing, how a little experiment 

 of his with Sweet Peas clearly demonstrated the true nature of reversion 

 and variation. Two well-grown dwarf races of Sweet Peas which breed 

 true, the prostrate ' Cupid ' and the half-dwarf ' Bush,' crossed together 

 produced the ordinary ' Tall ' Sweet Pea of full height. " The reversion 

 occurs because the two factors that made the height of the old Sweet Pea 

 again come together after being parted ; and the variations by which each 

 of the dwarfs came into existence must have taken place by the dropping 

 out of one of these elements or of the other." Here it may be said that 

 if the study of genetics had done nothing more than this, it would have 

 fully justified its existence, after the many years of vague and futile 

 discussions about reversion and variation since the time of Darwin. It is 

 refreshing to find that a simple experiment with Sweet Peas in Mr. 

 Bateson's garden at Grantchester should help to give us the solution of 

 two profound problems which have exercised the greatest minds in all 

 ages. 



In justice to Professor Bateson it seems only fair to point out 

 that though in his writings he modestly ascribes all his results to the 

 work of Mendel, those of us who have had the good fortune to work with 

 him know full well that there is much more than this behind it all. 

 Mendel's work with culinary peas has undoubtedly been the basis of all 

 recent genetic research, but had it not been for Professor Bateson's 

 guiding hand, would the problems of reversion and variation have ever 

 been solved ? I think not. 



Other interesting advances are noted in Professor Bateson's lecture, 

 such as the presence of preventive factors, of superposed factors, of mutual 

 repulsions and interactions between different factors, to say nothing of 

 some stimulating suggestions on the probable Mendelian inheritance of 

 sex in insects, birds and man. Last, but not least in importance, Professor 

 Bateson alludes to the value of genetic inquiry to the study of evolution 

 and to practical human affairs, and throws out some broad hints to those 

 who are concerned with the problems of the origin of species and the 

 betterment of the human race. 



In short this admirable and indispensable little book, written by a 

 master-hand, is essentially a popular work in the truest sense of the word, 

 and must appeal to all sorts and conditions of readers, in spite of its some- 

 what technical title. It is a book which makes for progress, and a careful 

 study of it is an absolute necessity to those who wish to be up-to-date in 

 the new science. 



" Through Southern Mexico : being an Account of the Travels of a 

 Naturalist." By Dr. Hans Gadow. 8vo., 527 pp., 165 illustrations and 

 maps. (Witherby, London, 1908). 18s. net. 



This is an interesting record of the author's travels and exploration 

 during some eight months in 1902 and 1904. There are plenty of travel 

 incidents and adventures, which give a very clear and vivid idea of a 

 country which is not often visited by English travellers. The special 



VOL. XXXV. G 



