12 Maurice Crozvthcr Hall ■ 



viously far afield. I believe Crawley has taken a logical position 

 in relating progression to the probable cause, — muscular activ- 

 ity, — and his statement of the modus operandi appears to me as 

 the most logical yet presented. In his second paper on this sub- 

 ject (1905) he states his case thus: "In the gregarine, the oscil- 

 lation of the protomerite is the conspicuous manifestation of mus- 

 cular activity, and under ordinary conditions of observations, the 

 only one which is seen. But it is always accompanied by the 

 wave on the surface of the deutomerite. The result is that a given 

 point on the gregarine's surface pushes backward and trans- 

 versely upon whatever may be in contact with it. This brings 

 about a movement of the entire animal in an opposite direction. 

 The movement will be rectilinear or zig-zag, dependent on the 

 greater or less extent of the transverse movement." 



The idea that I have arrived at in regard to gregarine pro- 

 gression accords with the above idea as I understand it. That 

 the contractile element, presumably fibers of some sort, in any 

 case, should be responsible for ordinary movement of any sort 

 would seem highly probable. It seems equally probable that when 

 a gregarine is progressing over a hard surface, the inner muscu- 

 lar impulse which brings about that progression should be trans- 

 mitted to that surface at the point of contact ; and one might rea- 

 sonably expect to find some movement of the gregarine body over 

 its contact surface. Since the gregarine commonly moves in a 

 straight line with the peculiar gliding motion, unaccompanied by 

 apparent muscular activity, which has called forth so much spec- 

 ulation and such remarkable theories, it is naturally to be ex- 

 pected that the actual movement by which the muscular activity 

 within is converted into a forward movement would be very 

 slight. And after all, this is quite in accord with another fact, 

 namely, that gregarines move with exceeding slowness. 

 Schewiakofif ( 1894) found that Gregarina mnnieri, the fastest 

 gregarine he had under observation, traveled t mm. in three min- 

 utes, and I have noted an equal speed for H. rigida, while the 

 white gregarine from Mclaiioplus would on occasion travel i mm. 

 in one minute and fifty seconds. Rut when one stops to consider 

 that H. rigida requires over seventy-five seconds tp travel a dis- 



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