128 PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE 



seems evident. Eventually theories will make way for facts 

 which will allow a proper perspective. 



Where do the results presented in the preceding pages 

 lead us? Does their value so far as their bearing upon 

 the production of new and transmissible characters that 

 will build up an organism in a required direction, consist 

 merely in the formulating of hypothesis after hypothesis 

 which as investigations proceed will in turn make way for 

 other hypotheses equally transient? Or on the other hand 

 do they mark a definite progress along the lines we are 

 endeavoring to follow, namely the control of evolution? 



Before attempting a reply which must prove more or 

 less unsatisfactory to those looking forward to immediate 

 results, it seems advisable to pause for a moment and in the 

 light of the preceding discussion consider the types of dif- 

 ferences — variations — that exist in so far as they may 

 affect the result with which we are chiefly concerned. 



Beginning at an early period in the history of evolu- 

 tion with the idea that all variations might be inherited, 

 results soon suggested that the characters due solely to 

 surrounding influences, such as food supply, etc., were not 

 thus transmitted. These were called fluctuating variations. 

 On the other hand variations due to the structural changes 

 in the germ cells were passed on from one generation 

 to another have been spoken of as inherited variations. 



The evidence at present indicates that farther subdi- 

 visions must be made and that normal inherited variations 

 consist of two quite distinct classes, the variations where 

 the results are due to the interaction of factors in accord- 

 ance with Mendelian principles and which, adapting a term 

 used by Plate (1913) may be called amphimutations, inas- 

 much as the condition is due to the mingling of two lines of 

 descent, the other all variations as a class in which the re- 

 sults — evolution in the abstract — are due to a series of units 

 added as increments, may well be called cumulations. It is 



