AIJTHOH S ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, OCTOBER 13 



THE RELATIONS BETWEEN NUCLEAR NUMBER, 

 CHROMATIN MASS, CYTOPLASMIC MASS, AND 

 SHELL CHARACTERISTICS IN FOUR PIECES OF 

 THE GENUS ARCELLA^ 



ROBERT W. HEGNER 



School of Hygiene and Public Health, The Johns Hopkins Universitxj 



FORTY-SEVEN FIGURES 



CONTENTS 



1. Introduction 1 



a. The problem 1 



h. Advantages of Arcella for nucleocytoplasmic studies 1 



c. Methods 4 



2. Experiments on Arcella dentata 4 



a. Experiments on binucleate members of family 150 4 



1. Introduction 4 



2. Results of removing part of the shell and part of the cytoplasm 4 



3. The reproduction of uninucleate pieces 5 



4. Empty shell formation and nuclear doubling 8 



5. Correlations 12 



6. Changes from binucleate to the uninucleate condition 14 



7. Reproduction of a uninucleate piece formed without an opera- 



tion, line 159 17 



8. Microdissection experiments IS 



6. Experiments on uninucleate specimens of family 150 21 



c. Experiments on members of family 152 27 



d. Experiments on members of family 58 28 



e. Summary of results of experiments on Arcella dentata 31 



^ The observations and experiments described in this paper were begun in the 

 zoological laboratory of the Johns Hopkins University on December 27, 1917; 

 were continued at the laboratory of the Brooklyn Institute of Arts and Sciences 

 at Cold Spring Harbor, Long Island, from June 17 to August 27, 1918, and were 

 completed at the School of Hygiene and Public Health of the Johns Hopkins Uni- 

 versity. The writer is indebted to the members of the Zoological Department 

 of the Johns Hopkins University for many courtesies and to Dr. C. B. Davenport 

 for the opportunity of carrying on work at Cold Spring Harbor. He is particu- 

 larly grateful to Prof. H. S. Jennings for his valuable counsel. Much of the sta- 

 tistical work was done by Dr. Ruth Stocking Lynch, instructor in Protozoology in 

 the School of Hygiene and Public Health. 



1 



