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Dr. H. M. Woodcock and Mr. G. Lapage. 



uneven (fig. 19). These peripheral movements of the protoplasm can perhaps 

 be compared, on a very small scale, with the wave-like movements of the 

 ectoplasm of Amoeba verrucosa. Next, the anterior portion of the body- 

 protoplasm on this side is moved as a whole backwards, around the central 

 part, as it were, carrying with it the anterior part of the flagellum and the 

 granules, and also, doubtless, the nucleus (cf. fig. 20). Finally, the creature 

 elongates again, having the anterior part of its body now where the posterior 

 part formerly was (fig. 21), and is ready to swim away in just the opposite 

 direction. 



Movements. — Helkesimastix possesses two distinct and characteristic methods 

 of locomotion. One, the more usual mode, is very interesting, because it is 

 Very difficult to explain ; in fact, we do not know quite how to explain it. 

 The creature glides forwards with a steady, almost unwavering movement, 

 the flagellum trailing behind in a straight line. While the rate of pro- 

 gression is not- as rapid as that of a Monas or a Bodo, for example, the 

 movement cannot by any means be called slow ; indeed, it is often 

 surprisingly fast, considering how little there seems to be to account for 

 it. There is certainly no vibration of the free, distal part of the flagellum 

 at all ; in this method of movement, the flagellum does not act as a 

 pulsellum. The creature is always at the surface of the medium when 

 moving in this way (or it is gliding along the under surface of the cover-slip), 

 the flagellum in both cases being uppermost. This fact leads us to think 

 that surface-tension plays some part in this type of movement. The body is, 

 as it were, suspended along its length to the flagellar thread, as a gymnast 

 may be suspended along a tight rope. The body is often seen to swing side- 

 ways partially around its flagellum, appearing then as in fig. 10 ; but it never 

 swings right above the flagellum. The only movement of the body which can 

 be noted is a very slight "knicking" movement of the anterior end, i.e. the 

 anterior end may make little tentative jerks from side to side, perhaps caused 

 by slight contractions of the anterior end of the flagellum. But the anterior 

 end of the body is not displaced laterally by more than half its width, if as 

 much, and the strength of these slight movements appears wholly insufficient 

 to produce the steady forward progression ; moreover, the creature may glide 

 for quite a considerable distance without even these. 



The other characteristic mode of progression occurs when an individual is 

 in the middle of the fluid, i.e. completely surrounded by it. Then it performs 

 vigorous, more or less undulatory movements of its whole body and flagellum, 

 the latter, as regards its applied portion, never becoming separated from the 

 body, and with its free, distal part lashing actively behind. The movement 

 of the body is very like that of a fish's tail, and not at all unlike the 



