THE CONSEEVATION OF LIFE 221 



division of labour of the single parts of the cell-body as we would 

 only expect to find in the highest multicellular organisms. 

 Indeed many of these Infusorians I will only mention the 

 trumpet-animalcule Stentor, the dainty bell-animalcules Vorticella 

 and Epistalis, the so-called shell-animacule Stylonycliia appear 

 to be so highly organized that no unprejudiced observer will 

 wonder at the founder of scientific protozoology, Ehrenberg, con- 

 tending that these animalcules possessed, like the multicellular 

 animals, an intestinal canal, nervous system, sexual glands, 

 muscles, kidneys, etc., and it is only quite recently that the 

 opinions of Dujardin and von Siebold, which perceived the 

 protozoa to be simple cells, were universally accepted (fig. 53). 



If we fill a glass with water and decaying leaves we shall 

 find after a few days a magnificent culture of Infusorians. This 

 will in most cases contain the slipper-animalcule (Paramcecmni), 

 one of the most widely distributed species. Under favourable 

 conditions of temperature and food the water becomes in a short 

 time filled with innumerable little white points. 



The Paramcecium reaches a length of about 0*2 to 0*3 mm. ; 

 we are therefore just able to see it with the naked eye. Its 

 shape is an asymmetrical oval, slightly flattened dorso-ventrally, 

 in which we can distinguish an anterior and posterior end. 

 While the former appears somewhat rounded the posterior end 

 is more or less pointed. The whole body-surface of Para- 

 mcecium is covered with an enormous number of delicate cilia 

 arranged in longitudinal rows, which during life almost inces- 

 santly carry out lashing movements and enable the animals 

 to dart skilfully through the water. We can best compare the 

 movements of the cilia to the uniform waving of a cornfield, 

 gently stroked by the wind, rising following falling; but just as 

 the ears are not always bent by the wind in -the same direction 

 so the play of the cilia changes from time to time in order to 

 drive the animalcule in another direction. 



The ciliation of the body is not quite regular in Paramcecium, 

 though more uniform than in many other Infusorians. Thus 

 we observe in the anterior end a flat groove, the so-called 

 ' peristomical area,' on which we find stronger cilia of somewhat 

 different shape. The posterior end is distinguished by some- 

 what longer cilia. 



