382 PROF. TH. W. ENGELMANN. 



" Especially in the latter case the plasmodium has often the 

 appearance of being composed of two quite different substances 

 — a streaming fluid filled with granules, and a viscous, slowly- 

 flowing portion, the former appearing to move within the 

 latter in special canals with firm walls. But new streams may 

 be often seen to arise in the transparent portion of the Plas- 

 modium, and the granules in a resting portion suddenly fall into 

 a main stream ; others, on the contrary, cease moving, and com- 

 pletely take on all the properties of portions which are at rest. 

 The resting granules on the margin of a strong stream can sud- 

 denly fall into movement, following the stream, and all sharp 

 line between streaming and resting portions vanish. 



" If one observes streams coming from the extremities of 

 branches one of two different phenomena may be seen. On 

 the one hand, the extremities, very much drawn inwards, pass 

 into a condition of energetic contraction, and the streaming is 

 most active near the extremities and diminishes in rapidity in 

 a centrifugal direction (towards the periphery). On the other 

 hand, the extremities from which the stream comes may sink 

 slowly together, and the rapidity of the stream increase steadily 

 in a centrifugal direction. 



" Where an active stream runs into the ends of branches, 

 and these rapidly swell up and new branches are given off, it 

 looks as though the granular mass were forcibly pressed into the 

 ends. At the same time, it is generally very obvious that the 

 stream going towards the ends of the branches increases in 

 velocity in a centrifugal direction ^' (pp. 47 — 48). 



According to Hofmeister,^ the granular stream of Myxo- 

 mycetes commences at the periphery and extends backwards 

 spreading as it does so; this may be also stated for numerous 

 cases of amoeboid movement and is of theoretical value. 



The streaming movement occurs in almost all Rhizopods, in 

 Heliozoa and Radiolaria, and in some Monads. Out of the 

 protoplasmic body spring long thin threads of protoplasm 

 — pseudopodia (root-feet). And as a rule upon the surface there 

 are a great number of fine granules in most active streaming 



1 W. Hofmeister, ' Die Lehre von der Pflanzenzelle,' p. 17, Leipzig, 1867. 



