REGENERATION AND CELL DIVISION IN 

 URONYCHIA 



GARY N. CALKINS 



FIFTEEN FIGURES 



CONTENTS 



Material and method 96 



Experimental 100 



1. Uronychia cells cut immediately after division 101 



2. Cells cut from fifteen minutes to one hour after division 102 



3. Cells cut from eight to sixteen hours after division, i.e., about midway 



between two divisions periods 103 



4. Cells cut during the process of division 105 



A. In the early stages and before the compact dividing nucleus is formed 105 



B. In the mid-phase of division 107 



C. If cut during the later phases of division 109 



D. If cut just prior to separation 110 



E. Cells cut two or more times during division Ill 



General 112 



Regeneration in Protozoa has been more or less exhaustively 

 studied by different observers, and Balbiani, Hofer, Gruber, Nuss- 

 baum, Verworn and others have contributed not a little to our 

 knowledge of the physiology of the cell through such experimental 

 work. So far as I am aware, however, no one has- studied the 

 regeneration power in relation to cell division, and it is generally 

 assumed that a protozoon is able to regenerate at all times with 

 equal facility. 



The experiments described in the following pages were made 

 during the summer of 1910 at the biological station at Roscoff, 

 Finistere, and I take this opportunity to express my grateful 

 thanks to Professor Yves Delage for the many courtesies shown 

 me while in his laboratory. 



THE JOURNAL OF EXPERIMENTAL ZOOLOUY, VOL. 10, NO. 2 

 FEBRUARY, 1911 



