SOME REMARKS ABOUT UNITS IN 



HEREDITY 



H Y w. J on AW Si: X 



COPKNIIAGEN 



THE Prol)lem of Heredity has been treated in somewhat different 

 ways by the several Hnes of biological research. The interests 

 and points of view^ in the different branches of the sciences concerning 

 Living Nature are not identical; hence we find rather different con- 

 ceptions of the processes and materials operating in Heredity. The ex- 

 perimental Biology and Physiology of modern times have reached con- 

 ceptions differing in principle from the conceptions of the mere de- 

 scriptive conventional »Natirral History» of old. 



The description of organisms, gathered in nature or marshalled in 

 collections, has created the terminologies of Botany and Zoology and 

 the art of such terminology is essentially morphological. The »charac- 

 ters» of the organism's, i. e. forms, special development, presence or 

 absence of composing »organs » and more or less autonomic structure- 

 elements in animals or plants, are the units with which classical Na- 

 tural History has mostly been operating. The anatomical and, later, 

 the histological analyses of organisms have mostly been carried through 

 in a morphological spirit; and the Cell-Theory gave in its time to the 

 cell the rank of an ultimate and (relative) independent »morphological 

 unit» of the bodies. The modern cytological nuclear analyses, the 

 chromosome-researches, have at any rate in their starting point a pure 

 morphological nature. 



Morphology dissects the organisms into special Parts, proceeding 

 towards a désintégration into smallest possible independent units of the 

 body. Regarding Heredity and Variability we see, for instance, 

 Weism.wn operating with the notion of smallest independently varying 

 parts of the organism (»selbständig variierende Teile»). For such 

 alleged units of the fully developed organism this prominent morplio- 

 biologist» supposed special organic representatives in the germplasm» 

 (»Keimplasma»), i. e. the total of those structural or constitutional ele- 

 ments in the sexual cells or fertilized ova etc., which for the zygote 

 in question determine the possibilities of development. 



