PKOPEKTIES OF VEGETABLE PEOTOPLASM 358 



changes in its surroundings, and is capable of adapt- 

 ing itself in various ways to such changed conditions. 

 In many cases the adaptation in question takes the form 

 of a spontaneous movement, in which the living substance 

 is concerned in a manner which seems to resemble the 

 behaviour of animal protoplasm. In others the response 

 to such changes presents itself to us as a modification of 

 the normal behaviour of the living substance with regard 

 to the vital processes we have examined, and in particular 

 to the entry of water into the vacuoles of the cells or its 

 transmission outwards. 



When we examine the phenomena of movement we 

 find that though evidence of contractility is procurable, 

 this phenomenon is of somewhat rare occurrence in plants. 

 Certain plants at particular times 

 emit from their body small masses of 

 naked protoplasm which are furnished 

 with a varying number of long fila- 

 ments (fig. 147). These filaments, 

 which are protoplasmic also, are 

 ordinarily in a state of active vibra- 

 tion, causing currents in the water Fia - 14 7. ZOOSPORB OF 



' fe . Ulothrix. x 500. 



in which they live, which float them 

 quickly from place to place. Among these free-swimming 

 protoplasts may be mentioned the zoospores of the Algae 

 and Fungi, and the antherozoids of these and higher plants. 

 The movement is a spontaneous one, the organisms being 

 endowed with the property of locomotion, which they exer- 

 cise in the discharge of their ordinary life-work. Though 

 put forth in the absence of any external stimulation, the 

 protoplasts are capable of receiving such impulses and 

 modifying the vibratile action accordingly. 



The mechanism of the movement is probably the con- 

 traction of each side of the filament or cilium alternately, 

 or of the part of the cell just at the point of attachment- 

 The impulse leading to the movement must be sought in 

 some decomposition originating in the protoplasm itself, 



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