220 H. M. WOODCOCK. 



Accorcliug to tlie manner in which they are produced^ two 

 kinds of movement, broadly speaking, can be distinguished : 

 (1) displacement of the body, usually rapid, and (2) movements 

 of flexion, extension, and contraction, often comparable to 

 '' euglenoid " movements. The latter are brought about, in 

 all probability, by the superficial myonemes above described 

 (cf. the muscle-fibrillte of Gregarines). 



In Trypanoplasma the anterior end always moves first 

 in displacement. According to Leger (1. c.) the principal 

 organ concerned is the undulating membrane, which, by its 

 rapid vibrations from side to side, is thrown into a series of 

 curves or folds; the effect produced is that of rapidly 

 succeeding waves, starting in front and running backwards.^ 

 The oscillations maybe continued into the posterior flagelkim, 

 which is then a subsidiary organ of locomotion, of the tjpe 

 known as a '^ pulsellum,'^ — i.e. it acts in a driving sense, like 

 the tail of a spermatozoon. Leger thinks, however, that this 

 flagellnm functions principally as a rudder. The anterior 

 flagellum is not greatly, if at all, concerned in locomotion. 

 During rapid displacement it is directed backwards, probably 

 passively carried along by the movement of the animal, only, 

 of itself, making slight wavy or circumrotatory movements. 

 At other times it seems to function rather as a sensitive 

 organ, being repeatedly thrust out, as it were, tentatively. 



' It may be noted that Ke3-sselitz (1. e.) takes a somewhat different view 

 of the manner in which displacement occnrs in Trj'panoph is. Ke3'sselitz 

 thinks that change of place is brought about by rapid, vibratile, or serpen- 

 tine movements of the whole body substance, the membrane acting, on the 

 contrary, as a curb or drag, which, of itself, would drive the animal in the 

 opposite direction. Tlie author bases his opinion on the observations of the 

 parasites in the attached phase, when the typical swimming motions are 

 often continued, and contends that were it not for this antagonistic working 

 of the membrane the parasites would be driven against their base and 

 swollen out of all shape. It may very well be that the membrane works in 

 an opposite sense at such a time (cf. next page) ; but it is rather unlikely 

 that the delicate body-substance can produce the vigorous movements shown 

 by the actively swimming parasites, when its only muscular elements are 

 perhaps myoneme tibrils i,cf. the slow progressive movement of Gregarines). 



