24 THE QUANTITATIVE METHOD IN BIOLOGY 



(colours, etc.) which often disappear in the collections after a 

 certain time. This method has been followed by Mr PH. 

 DAUTZENBERG (Paris), in whose princely collection of 

 shells the variation of numerous species is represented by 

 unrivalled series of specimens. 



It is, however, possible that the unusual conditions of life 

 which prevail under cultivation may result in a quantitative 

 modification of the living substance of certain specimens (note 2, 

 p. 20), or may produce, directly or indirectly, a qualitative 

 change — that is to say, a mutation. (See §§ 8a and 9.) 



It would be safer to have recourse to those hypotheses and 

 to use the terms sport, saltation or mutation only after we have 

 tried in vain to find another explanation. 



