^22 The Meohaiiism of Evolution- in Leptinotaksa 



Significant as are the investigations of Johannsen with the genotypes ol 

 plants and of Jennings in the clones found in Paramwcium with respect to these 

 problems, there still remains in both the idea of quantitative as opposed to quali- 

 tative " variations " bearing much the same relation to one another that they do 

 in the original De Vriesian statement. 



Siace most of us can not admit the possibility of any " specific biological prin- 

 ciple," or vitalistic content in the phenomena of our science, it follows that the 

 essential processes in one of the most evident phenomena of organism, the role 

 of heterogeneity in transmutation and evolution must be capable of expression 

 in terms and in principles that were equally applicable to both organized and 

 non-organized bodies ; and the same principles of investigation should, with dif- 

 ferences in the means employed, be applicable to and give consistent results in 

 both sets of material aggregations. This working hypothesis may be formulated 

 as follows : 



(1) The recognition that only physical principles are operative in the phe- 

 nomena classed as organic — a principle that is in entire accord with all of the 

 investigated and analyzed organic phenomena. 



(2) The recognition that the characteristics of organisms are of the same 

 origin and kind as in non-organized bodies and are specific properties, attributes, 

 and conditions, and have in organisms precisely the same origin and relation to 

 the whole that they do in non-organized masses. 



(3) The hypothesis that heterogeneity is the product of the composition of 

 the material by the conditions of the medium during the production of the com- 

 bination and influenced by the degree of purity of the combining materials and 

 presence of uncombined substances, which may influence the end-result in the 

 manifestation of specific properties and attributes, and be the active causes of 

 heterogeneity. These operations and results, when fully analyzed, will be 

 found to be but expressions of established principles of physical science. 



An analysis of heterogeneity must, therefore, be made on the following 

 scheme : 



(1) An analysis of the constitu,tion of the substance under standard con- 

 stant conditions of observation. 



(2) The determination of changes ia the medium upon constancy of the 

 substance. 



(3) The determination of loosely combined or uncombined "impurities" 

 in the organic system, and the role which they play in the production of fluc- 

 tuations in the characters of the material. 



(4) The isolation of non-fluctuating lines and study of the action of changed 

 conditions and introduced factors in the system, to determine the nature of the 

 so-called " fluctuations." 



The defect in biology is that homogeneity has been assumed without being 

 tested at all until recent years, and then inadequately. 



I began in 1904 an inquiry into this aspect of the " variation " problem, and 

 for this purpose I took the most variable and complex member of the group, 

 L. multitceniata Stal, which I was certain would give me no end of trouble and 

 present about all the complications that one would expect to find in any organ- 

 ized body. In this I was not deceived. 



It was recognized at the start that it was possible to obtain with the methods 

 in use an abundance of data, which could, with ingenuity, be arranged into 



