AUTHOR S ABSTRACT OF THIS PAPER ISSUED BY 

 THE BIBLIOGRAPHIC SERVICE, SEPTEMBER 15. 



REVERSIBILITY OF MORPHOGENETIC PROCESSES IN 



BURSARIA 



E. J. LUND 



From the Zoological Laboratory of the Johns Hopkins University and the Depart- 

 ment of Animal Biology, University of Minnesota 



THIRTY-EIGHT FIGURES 



CONTENTS 



I. Introduction 1 



II. The normal process of differentiation and dedifferentiation 2 



1. During cell division 2 



2. Before and after encystment 3 



3. Spontaneous dedifferentiation and differentiation 4 



III. Initiation of dedifferentiation and differentiation 5 



1. By cutting into two or more parts 5 



2. By mechanical injury without removal of parts of cell 6 



IV. Dedifferentiation and differentiation in heteromorphs 7 



1. Reversal of polarity in heteromorphic individuals from cut 



pieces 8 



2. Reversal of polarity in normal individuals 10 



V. Polarity, dominance and resistance of structures to dedifferentiation. 10 



VI. Dedifferentiation in other organisms 12 



VII. Role of reversibility in cell processes 13 



VIII. Relation of morphogenetic processes to hereditary constitution of 



Bursaria 16 



IX. Summary 17 



I. INTRODUCTION 



A review of the extensive literature on structural regulation 

 in organisms will show that the results have been obtained and 

 the theories to explain the phenomena have been formulated 

 from facts derived from studies on cell groups such as whole 

 individuals, organs or tissues. Little attention has been given 

 to the changes which must take place in the individual cell dur- 

 ing regulation. Few attempts have been made to contribute 

 an answer to such questions as: Just what changes take place in 



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THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 24, NO. 1 

 OCTOBER, 1917 



