732 MICROSCOPIC FORMS OF ANIMAL LIFE PROTOZOA 



proceeds entirely from a sort of trunk that soon divides into branches 

 which again speedily multiply by further subdivision, until at last 

 a multitude of finer and yet finer threads are spun out by whose 

 continual inosculations a complicated network is produced, which 

 may be likened to an animated spider's web. The protoplasm is 

 invested in a very delicate and closely applied envelope. Any small 

 alimentary particles that may come into contact with the glutinous 

 surface of the pseudopodia a.re retained in adhesion by it, and 

 speedily partake of the general movement going on in their sub- 

 stance. This movement takes place in two principal directions 

 from the body towards the extremities of the pseudopodia, and from 



these extremities back to the 

 body again. In the larger 

 branches a double current may 

 be seen, two streams passing 

 at the same time in opposite 

 directions ; but in the finest 

 filaments the current is single 

 and a granule may be seen to 

 move in one of them to its very 

 extremity, and then to return, 

 perhaps meeting and carrying 

 back with it a granule that 

 was seen advancing in the 

 opposite direction. Even in 

 the broader processes granules 

 are sometimes observed to come 

 to a stand, to oscillate for a 



J I V""" VY \ // Vk time, and then to take a retro- 



r.\ / \\ \ \ grade course, as if they had 



been entangled in the opposing 

 current, just as is often to be 

 seen in Chara. When a granule 

 arrives at a point where a fila- 

 ment bifurcates, it is often arrested for a time, until drawn into one 

 or the other current ; and when carried across one of the bridge- 

 like connections into a different band, it not unfrequently meets a 

 current proceeding in the opposite direction, and is thus carried back 

 to the body without having proceeded very far from it. The 

 pseudopodial network along which this ' cyclosis ' takes place is con- 

 tinually undergoing changes in its own arrangement, new filaments 

 being put forth in different directions, sometimes from its margin, 

 sometimes from the midst of its ramifications, whilst others are 

 retracted. Not unfrequently it happens that to a spot where two or 

 more filaments have met, there is an afflux of the protoplasmic sub- 

 stance that causes it to accumulate there as a sort of secondary centre, 

 from which a new radiation of filamentous processes takes place. 

 Occasionally the pseudopodia are entirely retracted, and all activity 

 ceases ; so that the body presents the appearance of an inert lump. 

 But if watched sufficiently long its activity is resumed, so that it 

 may be presumed to have been previously satiated with food, which 



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FIG. 570. Lieberkuehnia Wageneri. 



