1 8 THE PSYCHIC LIFE 



with the same activity; this activity continued for an 

 hour. 



We have now briefly examined the morphology of 

 the motor organs of Micro-organisms. 



It is very difficult to determine the physiological 

 process of the movements produced by these organs. 

 The simplest movements and the ones most easily un- 

 derstood, are those by which a cell suddenly and 

 strongly irritated withdraws its prolongations and as- 

 sumes a spherical form; this change of form can be 

 explained by a quick condensation of the protoplasm, 

 which becomes the seat of a phenomenon similar to 

 that of a contracting muscle. The sudden modifi- 

 cations which are observed to take place in the form 

 of the so-called metabolic Infusoria are in this way 

 explained by an analogous phenomenon, so much the 

 more evident as the Infusoria which possess this prop- 

 erty, show in the cortical layer of their protoplasm 

 (ectosarc) granulous bands which have with more or 

 less justice been compared to the muscles of the 

 higher animals. The displacements of the body de- 

 termined by the pseudopodia, by the vibratilp cilia, 

 and by the flagellum are much more difficult to inter- 

 pret; meanwhile it is probable that the movement 

 proceeds from the contractions of the protoplasm 

 which are produced either in the ectosarc or in the 

 motor organ itself; the latter is automobile, as is seen, 

 for example, when a flagellum separated from the rest 

 of the body continues to move in the liquid. 



It is well known that any number of discussions 

 have been raised as to the manner in which the ped- 

 icel on which the Vorticellae are mounted, contracts. 

 Still more obscure is the pscillatory movement of the 

 Bacteria. These small beings are very mobile when 



