Vol. 2 No. 5 



TORREYA 



May, igo2 

 THE ORIGIN OF SPECIES BY MUTATION* 



By D. T. MacDougal 



The period which has elapsed since the presentation by Darwin 

 and Wallace of the theory of the origin of species by natural 

 selection has been most fruitful in the development of specu- 

 lations as to the factors of evolution and the methods of inher- 

 itance and descent. The diversity of the evidence to be consid- 

 ered in connection with any phase of the subject is enormously 

 great, and the majority of biologists interested in the subject have 

 become engrossed in the argumentative presentation of the par- 

 ticular group of opinions to which they give a more or less 

 prejudiced and partisan adherence after the manner of a debating 

 society. During this period the investigators who most ration- 

 ally held to the attitude that the methods of the origin of species 

 were to be discovered by an examination of living forms them- 

 selves gave their attention to the comparative study of related 

 forms or to tracing the phylogenetic phenomena displayed in the 

 embryonic and juvenile stages of the organism. 



Within the last decade the conviction has been growing among 

 both botanists and zoologists that polemics, the array of recapitu- 

 lative facts offered by the organism in its younger stages, or the 

 facts of comparative anatomy might not offer any convincing 

 evidence of the manner by which the different species actually 

 have arisen, although the results of these studies have been of 

 enormous value in relation to other problems of biology. 



In these latter days the tendency has become marked to rely 

 more and more upon results obtained by experimental methods 



* Given before the weekly Convention, N. Y. Botanical Garden, April 16 and 23, 

 1902. 



LThe exact date of publication of each issue of Torreya is given in the succeed- 

 ing number. Vol. 2, No. 4, comprising pages 49-64, was issued April 12, 1902.] 



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