1905.] NATURAL SCIENCES OF PHILADELPHIA. 99 



was evidently present a ring-shaped mass of invisible jelly which was 

 continuous from the anterior to the posterior end of the gregarine. 

 In this case, although the conditions for observation were favorable, no 

 cause for the motion could be detected. I have also seen individuals 

 of Stenophora julipusilli exhibit this rotation. 



These phenomena, while not in any way explaining the cause of the 

 rotatory motion, show that it is not necessarily correlated with encyst- 

 ment. It is merely one of the several phases of the mobility of gre- 

 garines, ordinarily most conspicuously in evidence at the time of 

 encystmcnt. It has been the custom to separate these several phases 

 and to treat them as w^hoUy distinct phenomena. This custom I 

 believe to be unfortunate. It appears to me that all the motor phe- 

 nomena which the Polycystidea display may be directly credited to 

 contractions of the myocyte, with the possible exception of the amoe- 

 boid movements of certain species, and the rotation. For these 

 observational evidence is required before pronouncing a final decision. 



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BuTSCHLi, O. 1881. Kleine Beitrage zur Kenntniss der Gregarinen. Zeit. f. 



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 Crawley, Howard. 1902. The Progressive Movements of Gregarines. Proc. 



Acad. Nat. Sci. of Philadelphia, January, 1902, pp. 4-20, PI. 1, 2. 

 Delage et Herotjard. 1896. Traite de Zoologie Concrete. Tom. I, La 



Cellide et Les Protozoaires, Paris. 

 Leger et Duboscq. 1903. Recherches sur les Myriapodes de Corse et leurs 



Parasites. Archiv. de Zool. exper. et gen. [4], Vol. I, pp. 307-358. 

 Schewiakoff, V. 1894. Ueber die Ursache der fortschreitenden Bewegung 



der Gregarinen. Zeit. f. wiss. Zool, Bd. 58, pp. 340-354, Taf. 20 u. 21. 



