A Study of Some Gregarines ii 



may lie in the presence of circular concentric areas of varying 

 rigidity in the septum. 



In a mounted specimen I have seen what appear to be two dis- 

 tinct septa, and BiitschH (1882) records a similar observation. 

 This again is probably a mutant. 



The movements of gregarines have been the subject of con- 

 siderable discussion. It seems fairly certain, as Crawley (1905) 

 has observed, that since there is considerable variation in struc- 

 ture in different gregarines, a corresponding variation in the 

 cause of movements may be expected, and it may be that the 

 myocyte is contractile without being the only contractile element. 



Probably the most noteworthy feature of gregarine movement 

 is that of bodily progression or translation. This even, gliding 

 motion, unaccompanied by any seeming adequate manifestations 

 of energy, has called forth several theories of rriore or less prom- 

 inence and likelihood. These theories are briefly as follows: ( i) 

 Lankester (1872) referred the movement of Monocystis sipnncnli 

 to an "undulation of their lateral margins"; (2) Plate (T886) 

 thought that the gregarine took in part of the surrounding fluid 

 at one point and diffused it out ventrally, the diffusion forcing 

 the gregarine forward; (3) Frenzel (1891) regarded it as due 

 to a chemotactic attraction betvN^een the gregarine and intestinal 

 food masses, similar to molecular attraction or gravity; (4) 

 Schewiakoff (1894) believed that movement was due to an ex- 

 truded gelatinous thread which flowed posteriorly and, harden- 

 ing, pushed the gregarine ahead; (5) Porter (1897) suggested 

 that it was "probably caused by a very slight undulatory motion 

 of the under side of the animal"; (6) Magalhaes (1900) sug- 

 gested the following. "Le mecanisme de cette locomotion . . . 

 chez les Gregarines, je serais tente de I'attribuer a une fonction 

 propre, contractile, des fibres existant dans toute la longeur du 

 corps de I'animal, fibres rendues bien apparentes et bien revelees 

 par la striation reguliere longltudinale du corps"; (7) Crawley 

 (1902-5) attributes it to the action of the myonemes, though his 

 first statement was not very clear. 



Most of the theories quoted seem to me to have been adequately 

 answered bv writers on gregarines, and some of them are ob- 



159 



