i INSENSIBLE VARIATION 67 



by Bateson in a remarkable book, 1 has become deeply 

 significant and acquired great force since the striking 

 experiments of Hugo de Vries. This botanist, work 

 ing on the Oenothera Lamarckiana, obtained at the 

 end of a few generations a certain number of new 

 species. The theory he deduces from his experiments 

 is of the highest interest. Species pass through 

 alternate periods of stability and transformation. 

 When the period of &quot;mutability&quot; occurs, unexpected 

 forms spring forth in a great number of different 

 directions. 2 We will not attempt to take sides between 

 this hypothesis and that of insensible variations. 

 Indeed, perhaps both are partly true. We wish 

 merely to point out that if the variations invoked are 

 accidental, they do not, whether small or great, account 

 for a similarity of structure such as we have cited. 



Let us assume, to begin with, the Darwinian theory 

 of insensible variations, and suppose the occurrence of 

 small differences due to chance, and continually accumu 

 lating. It must not be forgotten that all the parts 

 of an organism are necessarily coordinated. Whether 

 the function be the effect of the organ or its cause, it 

 matters little ; one point is certain the organ will be 

 of no use and will not give selection a hold unless it 

 functions. However the minute structure of the 

 retina may develop, and however complicated it may 

 become, such progress, instead of favouring vision, 

 will probably hinder it if the visual centres do not 

 develop at the same time, as well as several parts of 

 the visual organ itself. If the variations are accidental, 



1 Bateson, Materials for the Study of Variation, London, 1894, especially 

 pp. 567 ff. Cf. Scott, &quot;Variations and Mutations&quot; (American Journal of 

 Science, Nov. 1894). 



2 De Vries, Die Mutationstheorie, Leipzig, 1901-1903. Cf., by the same 

 author, Species and Varieties, Chicago, 1905. 



