MOVEMENTS OF IRRITATION. 423 



are provided with cilia. We also find Vorticella?. The material 

 (hairs or infusoria) having been transferred to the hanging drop, 

 and the occurrence of movement having been proved, the current 

 of Hydrogen is at once started. I have often found it necessary to 

 continue the stream of gas for some time (sometimes for several 

 hours) before the movements ceased. The streaming of the proto- 

 plasm, and the free locomotion of the organisms, continues to take 

 place even in presence of minimal quantities of Oxygen. When 

 the protoplasm has at last become motionless, the state of asphyxi- 

 ation induced can be relieved again by passing a current of air. 8 



1 See Hauptfleisch in Priogsheim's Jahrbiicher, BJ. 24, p. 173. Kienitz- 

 Gerloff, Butan. Zeitung, 1893, holds the view that normally plasmic movement 

 takes place in every living cell. This result, which merits careful attention, he 

 arrives at partly from general considerations. If cells, removed from their 

 normal connections, at first exhibit no movements, this, according to Kienitz, 

 is the result of the mechanical injury. The matter requires further examina- 

 tion. 



4 See Berthold, Stadien iiber Protoplasmamechanik, Leipzig, 1886. 



3 Further investigation of these matters is out of place here. See Biifcschli, 

 V ntenuchunyen iiber Mikroskopische Schdunie (translated by E. A. Minchin) ; 

 Verworn, Bewegungen der lebenden Substanz, 1892; Detmer, Berichte der 

 Deutsclten butan. Gescllschaft, Bd. 10, p. 436 ; Engelmann, Ursprung der Muskel- 

 kraft, 1893. 



4 See Velten, Flora, 1876. 



3 See Sachs, Flora, 1864, p, 67. 



6 See Pfeffer, Zeitschrift f. ivissenschl. Mikro*k&pie r B<L. 7. 



7 See Sachs, Textbook of Botany. 



8 See also Clark, Berichte der Deatschen botan. Gesellschaft, Bd. 6, p. 273. 



169. The Free Locomotion of Lower Organisms (Movements of 

 Swarmers, etc.). 



Many of the lower plants, like typical animals, are capable of 

 free movement from place to place. The mechanism of these 

 movements is still not clear, and so we shall not closely consider 

 the matter. We ahall, however, attempt to demonstrate the 

 movements themselves, and determine how they are influenced by 

 external conditions. 



We will first take for examination Euglena viridis, which from 

 the morphological point of view is certainly not related to typical 

 algae but to the infusoria, but which, in more than one physio- 

 logical respect, is allied to the alga?. The material is easy to 



