CHAPTER VI. 

 THE PROBLEMS OF HETEROGENEITY. 



INTRODUCTION. 



In Chapter I it was shown that the characters of organisms are grouped under 

 three chief categories : the specific properties belonging to the specific living 

 kind, which can not be altered without change in the identity of the kind; 

 attributes, belonging to and distinguishing bodies of the same kind from one 

 another; and conditions, or states of being or activit}^ which can be changed 

 or removed without altering the identity of the body or its kind in any way. 



Since organisms have specific properties, attributes, and conditions, and 

 because evolution is entirely dependent upon change in the specific properties 

 through transmutation and secondary adjustments in the attributes and condi- 

 tions, it is important to understand what transmutation signifies and to dis- 

 cover as many of its modes of manifestation as possible before attempting to 

 produce new states or to recombine existing states into new kinds of living 

 substance. 



It is essential that by transmutation should be understood only those differ- 

 ences giving permanent change in the specific properties. Many of the differ- 

 ences found in any population — " variations " in the older terminology, and 

 which may give permanent changes which may be factors in evolution, are pro- 

 duced by metathesis through the rearrangements of the factors productive of 

 organic characteristics by the interbreeding of two more or less unlike types. 

 In this reaction, while differences in bodies and in substance may result, it is not 

 transmutation but heterogenetic rearrangement, which may or may not be 

 accompanied by transmutation. " Variation " in the older usage is synonymous 

 with the two divisions recognized here — i. e., the transmutation of qualities and 

 recombinations of existing characters into new complexes. The first is transmu- 

 tative heterogenesis, or the origin of new factors, the latter metatlietic hetero- 

 genesis or the rearrangement of existing factors. 



In nature, these two phenomena are continuously associated and active in the 

 production of the diversity of specific natural forms. It is necessary to untangle 

 the relations and interactions of these two methods of producing diversity before 

 proceeding with the problems of experimental evolution. All too often " vari- 

 ation " has been thought of as a process ; it is in reality devoid of unity of cause 

 and presents unity only in the diversity of end-results, a fact most clearly stated 

 by De Vries. 



If further progress is to be made in evolution investigations, it must be known 

 what the conditions of organisms in nature are, and these must, as far as possible, 

 be analyzed and determined by the methods of modern experimental 

 analysis in the laboratory. The latter will give us a glimpse of what may happen 

 in the population observed, and will give accurate knowledge of the way recom- 



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