PROCEEDINGS OF THE ACADEMY OF [Jan., 



THE PBOGRESSIVE MOVEMENT OF GREGARINES. 

 BY HOWARD CRAWLEY. 



I. Introduction. 



AVhile making observations on living specimens of Stenophora 

 juli,^ incident to a study of the life-history of this gregarine, I 

 became impressed by the fact that Schewiakoff's currently accepted 

 explanation for the progressive movement of gregarines does not 

 satisfactorily account for all of the phenomena which the animals 

 display. I was working at the time in the Zoological Laboratory 

 of Harvard University, and at the suggestion of the Director, 

 Prof. E. L. Mark, an investigation of gregarine movements of all 

 sorts was undertaken. I desire to take this opportunity to express 

 my sincere gratitude to Prof. Mark for the valuable aid which he 

 rendered me. 



The work was done almost exclusively on living animals, after the 

 method used by Schewiakoff, which will be described below. 

 Stenophora juli, from the intestine of Julus, and Echinomera 

 hispida, from the intestine of Lithobius, were the species studied. 



II. Historical and Critical. 



The movements displayed ;by gregarines are of two kinds. The 

 one, which consists of contractions of the body, is readily explain- 

 able by the existence of the muscular layer. The other, for which 

 I shall use the term progression, is a movement of translation, 

 during which the animal glides from place to place. It is usually 

 described as taking place without the slightest bodily movement. 

 This supposition, combined with the fact that gregarines possess no 

 motor organs, rendered their progression apparently causeless, and 

 until 1894, when Schewiakoff published his paper, it was regarded 

 as one of the unsolved problems of biology. Prior to this date, 

 biological literature contains but two suggested solutions of the 

 problem. Lankester (1872, p. 347) says: " On slitting up a large 



^ The nomenclature used in this paper is that given by Labbe (1899). 



