CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE 

 MUSEUM OF COMPARATIVE ZOULOGY AT HARVARD COLLEGE, 

 UNDER THE DIRECTION OF E. L. MARK. — No. 149. 



METABOLISM AND DIVISION IN PROTOZOA. 

 By Amos W. Petehs. 



Table of Contents. 



Page 



I. Introduction 441 



II. General Methods and Technique 444 



III. Conditions of Growth in Stentor, and the Management of Cultures . 449 



IV. Acceleration of Division 455 



V. Observations on Single Salts and Water 464 



VI. Discussion of Single Salts and Water 480 



VII. Observations on Single and Combined Salts 492 



VIII. General Discussion of Single and Combined Salts 490 



IX. The Permeability of Stentor 503 



X. The Extrusion of Color in Stentor 510 



XI. General Summary 512 



XII. Bibliography 514 



I. Introduction. 



The process of cell-division has been chiefly investigated for the sake 

 of determining the form-changes which characterize it. For this purpose 

 the descriptive-morphological method was found well adapted. The 

 present work deals with a different aspect of the same process and 

 employs a different method. Cell-division, being one of the fundamental 

 powers of organized matter, presents a variety of relations for study. 

 Its morphological aspect has naturally received attention first, but the 

 attempt at further analysis of the results has given rise to a new class of- 

 problems. This state of affairs is well summarized by Korschelt und 

 IJeider (:02, p. 253), who say: " Wir haben bei der Frage nach den 

 letzten Ursachen der im Vorstehenden beschriebenen Erscheinungen 

 immer auf den uns noch unbekannten Chemismus der lebenden Ele- 

 mente, auf unbekannte feinere Structuren oder auf den noch nicht 

 ergri'indeten Mechanisinus der Beweguiigser.^cheiiiungon verweisen mi'is- 

 sen." It is from the side of the first mentioned of these unknown, but 



