CHAPTER IV 



PROVOCATIVE BIOLOGICAL THEORIES 



In this closing lecture, it is fitting that we consider 

 those provocative biological ideas and theories which, 

 while they do not fit into the general scheme of our 

 former discussions, are, nevertheless, of great import in 

 understanding not only the incentives of future work in 

 the biological sciences, but in showing us why certain 

 paths of experimentation and discussion have been chosen 

 in preference to others. 



These ideas and theories, which are considered of great 

 importance by the outstanding workers of all lands, are : 

 the Organismal Theory, with some of its attempted ex- 

 planation such as the Organisationcentrum Theory, the 

 Axial Gradient (or Metabolic Gradient) Theory, the 

 Metabolic Theory of Sex, the Theory of Plasmogeny, and 

 the Theory of Emergent Evolution. 



The Organismal Theory. The founding of the cell 

 theory by Schleiden and Schwann, followed by the histo- 

 logical work of Bichat, had caused biological workers to 

 look to the individual parts of the organism, and pri- 

 marily to the cell, as the source of explanation for vital 

 phenomena. From about 1890 on, the older conception of 

 thinking of the organism as a whole again came into its 

 own. The foremost exponents of this Organismal Theory, 

 contrasted with the exponents of the Cell Theory as a 



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