1898] SOME NEW BOOKS 347 



the least, doubtful. Thus it is stated as a fact that hybrid plants are 

 " rare in a state of nature." Botanists are by no means agreed on this 

 point, and those who have made an exhaustive study of the flora of 

 limited areas, with special reference to this question, tend more and 

 more to the belief that hybridism is far from uncommon. On pp. 32 

 and 33, the whole argument is directed to showing that " we must 

 henceforth cease to regard " natural selection " as in any instance 

 the originating cause " of diversification in organic nature. Who 

 could ever have begun to regard it as such ? Individual variability 

 is the originating cause, whether the " sustaining cause " be natural 

 selection or physiological selection, or both, for it is admitted that they 

 may act together. 



Further, the method of argument is very imperfect. For example, 

 geographical isolation is constantly referred to and used as an illus- 

 tration of indiscriminate isolation, but it is not mentioned until the 

 last chapter, and then only quite incidentally, that " it belongs to the 

 very essence " of the author's view that " the efficiency of indis- 

 criminate isolation as a ' vera causa ' of organic evolution varies 

 inversely with the numlier of individuals {i.e., the size of the species- 

 section) exposed to its influence." The reader, therefore, whose 

 intelligence has enabled him to perceive that such a premiss was 

 essential, has up to this point been obliged to set aside as valueless 

 those statements from which it was omitted. This is a pity, but it 

 may, of course, be partly due to the fragmentary nature of the book, 

 of which only the first two chapters and the last were in type before 

 the author's death, as the editor (Prof. Lloyd Morgan) explains in the 

 preface. There are three appendices, wdiich do not add materially to 

 the value of the book. Altogether, we cannot think that " Darwin 

 and after Darwin" strengthens its author's position with regard to 

 his theory ; the latter must still be regarded as not proven, though 

 future evidence may modify this opinion. At present it cannot be 

 said that good cause is shown for considering physiological selection 

 as of paramount importance as a factor in evolution, or that the theory 

 gains much by this exposition. 



The Feeshwater Fauna of Bohemia 



Unteesuchuxgen uber die Fauna per Gewasser Bohmens. By Anton Fritscli and 



V. Vavra. Prag. : Fr. Rivnac, 1897. 



Des Anton Feitsch and V. Vavra have issued Part III. of their joint 

 researclies on the fresh- water fauna of Bohemia; this section deals 

 with the animals inhabiting the lakes known as the Schwarzer See 

 and the Teufelssee, as well as with the land-fauna and flora of the 

 neighbourhood of each. Their results are evidence of the excellent 

 work that may be done, without any very large outlay of money, by 

 setting up temporary portable zoological stations in little-worked 

 localities, and making thus a thoroiigh study of the fauna of a limited 

 area. Marine biological laboratories have already more than justified 

 their existence in England and other countries, and we should like to 

 see many more inland stations of the kind wdiich Bohemian enterprise 

 has made so successful. Especially is one needed in our own country, 

 but nobody seems inclined to go to work. During four years' work 

 in the neighbourhood of the lakes the investigations were very exact 



