PROTOPLASM 



21 



The observation of the phenomenon, as shown in the staminal hairs of Tradescantia , should be 

 made by every student. The hairs have only to be mounted in water under a cover-glass. The 

 ordinary species, T. virginica, is grown in most gardens. If the flowers of the greenhouse 

 species, T. discolor, are available, it will be easier to see the protoplasmic filaments, since the 

 cell-sap is colourless, instead of being of a purple colour as in T. virginica. 



The immediate cause of these movements seems to be changes of surface 

 tension, produced either by 

 outside influences or in the 



organism itself. The work -A \ JS 



of Rhumbler (1898, 1905) 

 may be referred to. 



A fact to be borne in 

 mind, in discussing the 

 behaviour of any organism 

 to external stimuli, is that 

 the response to similar 

 stimuli is not always pre- 

 cisely the same. There is, 

 so to speak, no fatal neces- 

 sity about the reaction. 

 This will be dealt with 

 more fully in Chapter XVI., 

 but the remark must be 

 made here that we are not 

 thereby compelled to assume 

 the presence of a controlling 

 "soul" or "Psyche." The 

 state of the organism itself 

 is by no means always iden- 

 tical. No stimulus, in other 

 words, meets with a react- 

 ing system in precisely the 

 same condition as a previous 

 one did. 



A sea anemone, which has 

 been without food for some time, 

 reacts rapidly to bits of crab 

 meat, seizing them with its ten- 

 tacles and pushing them into its 

 gastric cavity. As repeated por- 

 tions are presented, the reaction 

 becomes gradually more inert, 

 until finally no reaction is ob- 

 tained at all. The presence of 

 food in some way prevents the 

 taking of more (Jennings, 1906, 

 pp. 225-236). We are irresis- 

 tibly reminded of a reversible, 

 or balanced, chemical reaction 

 becoming slower and slower as 

 equilibrium is approached (see 

 Chapters VIII. and X.). This 

 is made the more striking by the 

 fact that pieces of filter paper, 

 which produce no chemical 

 change in the organism, con- 

 tinue to be pushed into the gastric cavity as long as they are presented, although there is no 

 room for them, and they are immediately disgorged. 



Pages 111-127 of Jennings' Carnegie publication (1904), dealing with "Physiological States 

 as Determining Factors in the Behaviour of Lower Organisms," should be read. 



We have seen how portions of a protoplasmic organism, such as Badhamia, 

 when separated by passing through cotton wool, subsequently coalesce again. 

 The same thing occurs when the separate amoebae, proceeding from germinating 



FIG. 19. CELLS OF STAMINAL HAIRS OF TRADESCANTIA, 

 COPIED EXACTLY WITH CAMERA LDCIDA. 



A, normal, in water. 



B, the same cell, after moderate, local, electrical stimulation. The 



region of the excited protoplasm extends from a to b. c, proto- 

 plasm contracted to round lumps and balls, d, pale vesicles. 

 Length of cell, 0'2 mm. 



(Kiihne, 1864, fig. 3.) 



