PEOTOPLASMIO MOVEMENT. 



385 



2. Movements of Protoplasm bounded by firm 

 Integuments. 



This case is chiefly realised in vegetable cells. We can with 

 the botanists distinguish two chief varieties : — Circulation and 

 Rotation. 



Circulation. — Here contractile protoplasmic threads 

 stretch inwards from the cell wall, traversing the cell space, 

 which is filled with fluid ; they vary in number and are con- 

 tinually changing their position, form, and size. The direction 

 and rapidity of their movement are generally inconstant, being 



Fig, 2. — Cells from the staminal hairs of Tradescantia (after Kilhne). 

 A. Fresh, in water. B. The same cell after slight local electrical stimu- 

 lation, a — b. The region stimulated, c. Clumps and nobs of contracted 

 protoplasm. 



