8 



BOTANY. 



The formation of the new current may be explained as follows : 



Let A B be a stream in which the movement is from A 



to B ; clearly there will be an aggregation of protoplasm about B. 

 When the current in the direction A B stops, the new one, in the 

 reverse direction, B A, begins at A, by the movement toward it of the 

 particles nearest to it ; next the particles further off move toward A ; 

 after this, those still further off, and so on. The current extends back- 

 ward. So, too, when a stream begins de now, it is propagated back- 

 ward from the point of beginning. 



8. Mass-Movement (Amosba-Movement). In the flowing 



back and forth in the 

 streams the movement 

 may be greater in one 

 direction than in the 

 other ; this causes a 

 slow motion of the 

 whole plasmodium in 

 the direction of 

 the greatest movement. 

 When this takes place 

 in the case of streams 

 which begin in the mar- 

 gin of the plasmodium, 

 protuberances of vari- 

 ous shapes arise ; these 

 may be extended into 

 branches (pseudopQ- 

 dia), which may again 

 be branched one or 

 more times. By the 



J? 12 D. UUUUie "1 piarillWUlum. WA AS*wyrrv*i"rtv f * jl 



eerpula forming pseudopodia. The heavy black anastomosing OI these 

 line indicates the outline at the beginning oi the 



observation ; the pseudopodium a-b formed in 8 brandies a Complex 



seconds, c-d in 30, and c-e in 55 seconds. X 10. ^ plvincmio- 



After Hofmeister. moving aild Ciianglllg 



network is formed. (See Fig. 140, page 208) There is pos- 

 sibly to be separated from the above-described mass-move- 

 ment that more or less rapid change of external contour 

 which has, from its resemblance to the motions of the 

 Amoeba, been denominated the Amoeba-movement (Fig. 6). 

 It is best observed in the so-called "Amoeba-form " stage of 

 the swarm-spores of the Mvxomycetes. 



Fig. 6. Outline of a plasmodium of Didymium 



