APP 8 1205 



SCIENCE 



A WEEKLY JOURNAL DEVOTED TO THE ADVANCEMENT OF SCIENCE, PUBLISHING THE 

 OFFICIAL NOTICES AND PROCEEDINGS OF THE AMERICAN ASSOCIATION 

 FOR THE ADVANCEMENT OF SCIENCE. 



Friday, April 7, 1905. 



CONTENTS : 

 The Muta tion Theory of Organic Evolution : — 

 From the Standpoint of Animal Breeding: 

 Professor W. E. Castle 521 



From the Standpoint of Cytology: Pro- 

 fessor Edwin G. Conklin 525 



Mutations: Professor Thomas Dwight. . 529 



Systematic ^York and Evolution : Professor 



L. H. Bailey 532 



Ethology and the Mutation Theory: Pro- 

 fessor William Morton Wheeler 535 



Discontinuous Variation and the Origin of 

 Species: De. D. T. MacDougal 540 



Scientific Books: — 



The Zoological Record: Professor T. D. A. 

 CocKERELL. Dantec's Les lois naturelles: 

 Dr. W. H. Sheldon 543 



Societies and Academies: — 



The New York Section of the American 

 Chemical Society: Dr. F. H. Pough 547 



Discussion and Correspondence : — 



The Naturalist's Universal Directory: G. K. 

 Gilbert. An Overlooked Form of Stereo- 

 scope: Professor Frank P. Whitman. 

 Kilauea again Active: Professor C. H. 

 Hitchcock 548 



Special Articles: — - 



The Prairie Mounds of Louisiana: Pro- 

 fessor E. W. Hilgard. Progress in the 

 Study of the Eelep: 0. F. Cook 551 



Quotations : — 



The Sanitation of the Panama Canal Zone. . 554 



Botanical Notes: — 

 A Helpf ul Bulletin ; Seashore Laboratories ; 

 Utah Fungi; Photographs of Vegetation: 

 Professor Charles E. Bessey 555 



Scientific Notes and News 556 



University and Educational News 559 



MSS. inteuded for publicatiou aud books, etc.. intended 

 for review should be sent to the Editor of Science, Garri- 

 Bon-on-Hudson, N. Y. 



THE MUTATION THEORY OF ORGANIC 

 EVOLUTION.'' 



The Mutation Theory of Organic Evolu- 

 tion, from the Standpoint of Animal , 

 Breeding: W. E. Castle, Assistant Pro- 

 fessor of Zoology, Harvard University. 

 The mutation theory, as I understand it, 

 is not designed to replace Darwin's theory 

 of natural selection, nor is it capable of 

 replacing that theory. Natural selection 

 must still be invoked to choose between 

 different organic forms, preserving the 

 more efficient, destroying the less efficient. 

 The question raised by this new theory is, 

 AVhat sort of forms are subjected to the 

 action of natural selection? Is there a 

 complete gradation of forms between two 

 extreme conditions and is natural selection 

 called upon to choose from this whole series 

 the one which is organically most efficient, 

 or is the task simpler and is the choice 

 made merely between two widely separated 

 conditions of the ideal series? Thus, we 

 find within a species two varieties, one 

 larger than the other. Have they diverged 

 by gradual cumulation of minute differ- 

 ences in size, or by a single step? These 

 alternative views are known, respectively, 

 as the selection theory and the mutation 

 theory. Both views were recognized by 

 Darwin as possibilities, though he seems to 

 have attached more importance to the proc- 

 ess of gradual modification. Most of his 

 followers have given attention exclusively 

 to this process, but a few, like Bateson and 

 de Vries, have regarded modification by 



* Six addresses given before the American So- 

 ciety of Naturalists at Philadelphia, December 28, 

 1005. * 



