ON BIASTREPSIS IN ITS RELATION TO CULTIVATION. 



t. In his very suggestive volume 'Materials for the Study of Varia- 

 tion, treated with especial regard to Discontinuity' (1894) Mr. W. 

 Bateson says (p. 574), with regard to the relation of the study of 

 variations to the great questions of the origin of species and the 

 operation of natural selection: The only way in which we may 

 hope to get at the truth is by the organization of systematic experi- 

 ments in breeding, a class of research that calls perhaps for more 

 patience and more resource than any other form of biological in- 

 quiry. Sooner or later such investigation will be undertaken and 

 then we shall begin to know.' 



It is hardly necessary to point out that such experiments in 

 breeding can be much more easily carried out with plants than with 

 animals, especially when it is necessary to have a large number of 

 individuals under observation. This is the case at present, since 

 selection is the chief point at issue, so that the validity of the con- 

 clusions to be drawn depends mainly on the number of the indi- 

 viduals in each experiment. In the case of plants it is a simple matter 

 to raise several hundred individuals and to retain but a few as 

 the parents of the succeeding generation; it is a much more com- 

 plicated and costly affair to do this in the case of animals. Moreover, 

 it is easy to cultivate plants under quite natural conditions, whilst 

 the breeding of rats and mice or moths or other insects, for experi- 

 mental purposes, can only be carried on under conditions which 

 are far from being natural and which cannot be said to be favou- 

 rable to the normal development of the animals. On these and 

 other similar grounds breeding experiments relating to inheritance 

 and variation can be most satisfactorily instituted with plants. 



For more than ten years I have been occupied with experiments 

 of this nature. The object which I have had in view is to study 

 the effect of selection under the most favourable conditions in pro- 

 ducing breeds and varieties, on the one hand; and, on the other, 

 the influence of various external conditions upon the production 

 and further development of these variations. 



In the course of such experiments the important distinction to 

 be drawn between individual and partial variations becomes at 



