THE REACTIONS OF THE FLAGELLATE PERAXEMA 



S. (). MAST 



Tin Johns Hopkins University 



One figure 



Peranema is a colorless, cigar shaped flagellate scarcely 0.05 

 mm. long and but little more than 0.0 1 mm. in diameter. A 

 prominent contractile vacuole is found near the anterior end 

 from which projects a heavy flagellum nearly as long as the 

 body, Fig. 1. It is a hardy, sluggish creature, usually found 

 in abundance in cultures rich in decaying organic matter. I 

 have kept specimens in excellent condition for three weeks on 

 a slide under a cover glass sealed air-tight with vaseline. These 

 flagellates ordinarily move in contact with solid objects or on 

 the surface film, but sometimes they swim through the water 

 verv much like Euglena. I shall refer to the former method 

 of locomotion as crawling. The rate of motion by either method 

 is relatively slow, the crawling rate being only 1.3—2.6 mm. per 

 minute and the swimming rate but very little more. Owing to 

 this very moderate rate of locomotion it is a simple matter to 

 follow under high magnification every movement the animal 

 makes. 



In crawling, Peranema is frequently seen to continue for 

 considerable distances in a fairly straight line. It does not 

 rotate as it does in swimming but proceeds with a given surface 

 continuously in contact with the substratum to which it adheres 

 with considerable tenacity, probably by means of secreted 

 mucus. The flagellum extends straight forward and is rigid 

 and motionless except for about one-sixth of the whole at the 

 tip, which is bent at right angle so as to form a sort of hook, 

 Fig. 1 . This bent part of the flagellum vibrates rapidly, striking 

 backward and forward in such a way that the free end describes 

 a narrow' ellipse. Thus the creature is literally drawn slowlv 

 and steadily along. This is the method of locomotion that is 

 ordinarily seen but if the animals are strongly stimulated, as 

 by the addition of a little iodin, marked wave-like contractions 

 are seen to pass over the body from the posterior to the anterior 

 end. That this wave-like contraction is at least at times func- 



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