TABLE OF CONTENTS 



PAGE 



INTRODUCTION i 



PART I. THE PROBLEM OF ORGANIC CONSTITUTION 



CHAPTER 



I. VARIOUS THEORIES OF THE ORGANISM 9 



Neo-vitalistic Theory; Corpuscular Theories; Chemical Theory; 

 Physico-chemical Theory; The Colloid Substratum of the Organism; 

 The Relation between Structure and Function; References. 



II. THE LIFE CYCLE 34 



Growth and Reduction: Definitions of Growth and Reduction, The 

 Nature of Growth and Reduction; Differentiation and Dedifferentia- 

 tion: Differentiation, Dedifferentiation; The Basis of Senescence and 

 Rejuvenescence; References. 



PART II. AN EXPERIMENTAL STUDY OF PHYSIOLOGICAL SENES- 

 CENCE AND REJUVENESCENCE IN THE LOWER ANIMALS 



III. THE PROBLEM AND METHODS OF INVESTIGATION .... 63 



The Nature of the Problem; Susceptibility in Relation to Rate of Metab- 

 olism; The Direct Method; The Indirect Method; Other Methods; 

 References. 



IV. AGE DIFFERENCES IN SUSCEPTIBILITY IN THE LOWER ANIMALS . 92 



The Experimental Material; Age Differences in Susceptibilty in Pla- 

 naria maeulata; Age Differences in Susceptibility in Planaria 

 dorotocephala; Age Differences in Susceptibility in Other Forms; 

 Conclusion; References. 



V. THE RECONSTITUTION OF ISOLATED PIECES IN RELATION TO RE- 

 JUVENESCENCE IN Planaria AND OTHER FORMS 103 



The Reconstitution of Pieces in Planaria; Changes in Susceptibility 

 during the Reconstitution of Pieces; The Increase in Susceptibility in 

 Relation to the Degree of Reconstitution; The Susceptibility of Ani- 

 mals Resulting from Experimental Reproduction and Sexually Pro- 

 duced Animals; Repeated Reconstitution; References. 



VI. THE RELATION BETWEEN AGAMIC REPRODUCTION AND REJU- 

 VENESCENCE IN THE LOWER ANIMALS 122 



The Process of Agamic Reproduction in Planaria dorotocephala and Re- 

 lated Forms; The Occurrence of Rejuvenescence in Agamic Reproduc- 

 tion in Planaria dorotocephala and P. maeulata; Agamic Reproduction 

 and Rejuvenescence in P. velata; Agamic Reproduction and Re- 

 juvenescence in Stenostomum and Certain Annelids; The Relation be- 

 tween Agamic Reproduction and Rejuvenescence in Protozoa; Agamic 

 Reproduction and Rejuvenescence in Coelenterates; References. 



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