DEDIFFERENTIATION IN ECHINUS LARV.E, AND ITS 

 RELATION TO METAMORPHOSIS. 



J. S. HUXLEY, 

 NEW COLLEGE, OXFORD. 



CONTENTS. 



1. Introduction 210 



2. Differential modification of growth . . 210 



3. Dedifferentiation of larvae 212 



4. Experiments on recovery 218 



5. On the general effect of mercury in weak solutions 221 



6. Discussion (A) Maintenance of form 223 



(B) Dedifferentiation and metamorphosis 224 



(C) Axial gradents and surface-effects 227 



(D) Previous references 229 



(E) Recovery 229 



7. Summary 231 



8. Literature list 232 



9. Description of figures 235 



i. INTRODUCTION. 



The following observations and experiments were made at the 

 Marine Biological Association's Laboratory at Plymouth in July 

 and August, 1920. 



The accidental discovery that dedifferentiation, of a type simi- 

 lar to that already studied in Clarcllina, occurred in Echinoderm 

 larvae led me to make further observations on this phenomenon. 

 Owing to lack of material, they are very fragmentary. I hope 

 to resume them at the earliest opportunity. Meanwhile their 

 theoretical bearing on the question of metamorphosis warrants 

 their publication in their present form. 



I have to thank the Director and Staff of the Plymouth Labora- 

 tory for their assistance. The work was carried on with the aid 

 of a grant from the Royal Society. 



2. DIFFERENTIAL MODIFICATION OF GROWTH. 

 Experiments were started on fertilized eigs of Echinus miliaris 

 in order to test certain conclusions of Child's C'i6 and '17) as to 



210 



