AN ANALYSIS OF THE PROCESS OF REGENERATION 

 IN CERTAIN MICRODRILOUS OLIGOCHAETES 



LIBBIE H. HYTVIAN 



Hull Zcological Laboratory 



TWENTY-FOUR FIGURES 



CONTENTS 



I. Material 100 



II. The axial gradient 101 



1. The cyanide method 101 



2. The primary gradient 105 



3. The gradient of the naids 112 



4. The gradient of Lumbriculus inconstans 119 



5. The gradient of the tubificids 120 



6. The gradient in embryos 120 



7. Summary 123 



III. The data of regeneration 124 



1. The head region of oligochaetes 124 



2. General considerations on regeneration in oligochaetes 126 



3. Regeneration in Dero limosa 130 



4. Regeneration in Lumbriculus inconstans 133 



5. Regeneration in the tubificids 141 



6. Summary 142 



IV. Analysis of the regenerative process 143 



1. The time of head determination 143 



2. Stimulation by section 145 



3. General conception of the process of regeneration 150 



V. Summary 158 



VI. Bibliography 161 



The importance of regeneration as an experimental method 

 has not been sufficiently recognized. The nmnerous investi- 

 gations which have been carried on in this field have given us a 

 vast amount of data regarding the capacity for regeneration of 

 all groups of animals, the axial differences in rate and amount of 

 regeneration, the histology of the process, and so on, but little 

 progress has been made in the interpretation and analysis of the 

 facts observed. Child ('11 d) has pointed out the fundamental 

 biological significance of regulatory phenomena, and has shown 



99 



