320 



THE AMEBIC AX NATURALIST [Vol. XLIII 



species-forming and adaptation. His detailed account and rea- 

 soned criticism of De Vries's famous theory are admirable. 

 Isolation, especially those forms of it which may be classified 

 under the general head of ' 'Biologic isolation," is treated in 

 extenso. In this connection Plate opposes those statements of 

 Wagner and D. S. Jordan, which claim that new species do not 



, or do so onlv 



geographic range. 



He refers to the hundred Gammarus species in Lake Baikal, the 

 numerous Cladoceran species of Bythotrephes in the Caspian 

 Sea, and the eighty or more chromid kinds in Lake Tanganyika, 

 as examples of nearly related forms that have long inhabited 

 the same Ijmited region and yet among which evolution has 

 steadily gone forward. He discusses the old question of the 

 inheritance of acquired characters in a new wav, and those 

 pages in which he explains and justifies his admission of the 

 logical necessity of such an inheritance to explain certain tvpes 

 of adaptation constitute one of the most important parts of the 

 book. His treatment of the Darwinian theory of sexual selec- 

 tion and candid admission of its weaknesses is another ad- 

 mirable instance of the broad-mindedness of this Darwinian 

 champion. Finally his account of the objections to selection and 

 their refutation or recognition as partly valid is simply com- 

 plete, as is his consideration of the species-forming theories 

 auxiliary to selection. 



But this fugue of praise grows monotonous, and yet it is hard 

 to introduce any new measure. Perhaps the sparse scattering 

 of pictures may be criticized as being far too meager if illustra- 

 tion was really needed, and easy reading of the text is a little 

 interfered with by the introduction of date and page references 

 into the lines; but these are trifles. The book is excellent ar- 

 ranged both for logical sequence of presentation and for easy 

 reference to any particular phase or topic of the wide subject 

 treated. Professor Plate's acquaintanceship with the active 

 work now going on along the various lines of evolution study 

 and with the literature of the whole subject is manifestly nearly 

 exhaustive. It is especially pleasant to note his generous recog- 

 nition of American work. 



