THE OTTAWA NATURALIST 



VOL. XXIIl. OTTAWA, SEPTEMBER, 1909 No. 6 



CERTAIN BIOLOGICAL PRINCIPLES AND THEIR PRAC- 

 . TICAL APPLICATION IN THE IMPROVEMENT 

 OF THE FIELD CROPS OF CANADA. 



By L. H. Newman, B.S.A., Secretary, Canadian 

 Seed Growers' Association, Ottawa. 



(Continued from page 91) 



THE MUTATION THEORY. 



From the evidence brought forth in connection with the 

 theories held by biologists since Darwin's time, it is apparent that 

 the efficacy of natural selection and of the use of fluctuating 

 variations in explaining the facts of evolution, have been steadily 

 losing ground. On the other hand there has been a gradual 

 tendency to regard the part played by "discontinuous" varia- 

 tions or "mutations" as being of more importance in this con- 

 nection. The supporters of the latter idea have received much 

 encouragement from the work of DeVries of Amsterdam, which 

 work with that of Mendel has served to place the problems of 

 heredity in an entirely new light. The law of Mendel respecting 

 the transmission of characters when two plants are crossed is 

 a large subject in itself and shall not be discussed now. Suffice 

 it to say that the hybridization of varieties as effected in the 

 light of this law is probably the most potent means of producing 

 new varieties that is now within the reach of the expert breeder. 

 The work of DeVries is worthy of special consideration since his 

 discoveries may be said to have marked a new epoch in the long 

 line of investigations of the factors in evolution. 



DeVries' idea is that plants and animals are made up of 

 "distinct units" which correspond to atoms in chemistry. By 

 crossing one individual with another the units involved may be 

 combined but never split, just as combinations may be made in 

 chemistry. Transitional forms do not exist between the elements 

 themselves, which assumption goes to support the theory of 



