186 



tions and arguments are futile in dealing with a problem the solu- 

 tion of which is directly accessible to the experimentalist. 



The author's general position could hardly be better expressed 

 than by the following, final paragraph of his book. " If we sup- 

 pose that new mutations and ' definitely ' inherited variations 

 suddenly appear, some of which will find an environment to which 

 they are more or less well fitted, we can see how evolution may 

 have gone on without assuming new species to have been formed 

 through a process of competition. Nature's supreme test is sur- 

 vival. She makes new forms to bring them to this test through 

 mutation, and does not remodel old forms through a process of 

 individual selection." 



The essential feature of the book, and the one that constitutes 

 its chief claim to attention consists in the fact that the author has 

 brought the accumulated data of his extended researches upon 

 growth and regeneration to the test, and finds that the theories 

 of natural selection, inheritance of acquired characters, and origin 

 of new forms by direct adaptation are inadequate in their interpre- 

 tation, while the results in question are entirely in accord with 

 evolutionary procedure by mutation, or discontinuous variation. 

 The power to replace lost organs, or rebuild tissues that have 

 been destroyed, the possession of useless or injurious organs, and 

 the incipient stages of a new organ, or the atrophied form of an 

 old organ may be accounted for by mutation, while the interpre- 

 tation of these features has been one of the ever present difficulties 

 in maintaining the theory of natural selection. The author, as 

 may be seen from the above, is therefore in practical accord with 

 de Vries, the results of whose recent experiments he discusses in 

 detail. 



Professor Morgan has certainly invited grave adverse criticism 

 on certain features of his book. The subject involves a rigid analy- 

 sis of phenomena of both animal and plant life, yet we do not find 

 that any botanist passed upon the validity of the botanical state- 

 ments, so far as the acknowledgments in the preface may be 

 relied upon. A perusal of the volume reveals ample confirma- 

 tion of this fault in the preparation of the book. To say that the 

 color of a flower is a device that secures the visits of certain in- 



