312 MENTAL FACULTIES sec. 



movements of the protoplasm, whicli are themselves the result 

 of the reaction, which has become regular, of the protoplasm 

 to stimuli. Such, for instance, are obviously the movements 

 of the cilia of ciliated cells, so far as these are not affected by 

 nerves. The forward movement of the spermatozoa of the 

 toad and of the salamander is caused by rhythmical streamings 

 of the protoplasm succeeding one another like waves, and I 

 have shown that this rhythmical motion occasionally passes 

 into the amceboid,-^ so that we have some OTound forrerardiuo- 

 the latter also as involuntary, although it appears to be 

 voluntary. In fact, I cannot accommodate myself to the idea 

 that the amoeboid cells which wander about like amoebae in 

 our blood-vessels and throughout our bodies are independent 

 beings endowed with sensation and will. 



Botanists have made more investigations than zoologists 

 into the stimuli which cause locomotion in the lower 

 organisms, or w^hich accelerate or give a definite direction to 

 their movements, movements which at first sight appear to 

 be altogether voluntary. I will quote here an instance of 

 the first case ; another of no less importance is aftbrded by 

 the experiments of Pfeffer, discussed on p. 334. 



The movement of Myxomycetes is influenced by-: — 

 1. Moisture (Hydrotropism) : In their young stages they 

 wander from the parts of the substratum {i.e. of the deposit 

 on which they are creeping), which are gradually drying up, 

 towards those which continue moist longer ; " it is even 

 possible, by bringing moist bodies into the proximity of any 

 ramifications, to cause the production of pseudopodia, which 

 elevate themselves from the substratum, and soon come into 



^ Th. Eimer, Unters. ilber d. Bau u. d. Beioegunci der Samenfdden, o^j. cit. 

 Accordingly the ultimate cause of the motion of the spermatozoa of the Mam- 

 malia also must lie in amoeboid movements in constant directions. With regard 

 to ciliated cells compare the following. 



- E. Stahl, Zur Biolorjie der Myxomyceten, Botan. Zeitung, 1884, No. 10-12. 

 Abstract in Sitzv.nrjsbericht der Jenaischen Gesellschaft fur Medizin und Naivft- 

 wissensch. 1883, Sitzung vom 16th November. 



