74 



GENERAL BIOLOGY 



where several may be observed together, the movements of 

 all somewhat restricted. Note the perfect definiteness of 

 anterior and posterior ends of the body. Note the general pli- 

 ancy of the body, best seen when turning sharp corners, etc. 



5. Observe the presence of a sharply defined layer of 

 ectosarc, thickly covered over its outer surface with minute 

 transparent hair-like processes called cilia in constant rapid 

 motion. To the lashings of these cilia, the movements of 

 the animal are due. The cilia are invisible in too strong 

 light, and also when in rapid motion; in the latter case the 

 scattering of such minute particles as come near them will 

 testify to their presence and activity. A few longer cilia at 

 the hinder end of the body, seem to serve as a sort of steer- 

 ing apparatus or rudder, and probably assist in keeping to a 

 true course in swimming. 



6. Observe the position and relations of the oral groove, 

 its length, its oblique position, and the funnel-shaped depres 

 sion in which its posterior end terminates. Observe the 

 peristome surrounding the mouth , bearing a continuous line 

 of larger and stouter cilia, which, besides their participation - 

 in the spiral swimming, drive food particles into the funnel- 

 shaped mouth opening. 



7. Mount a small drop of clean water containing para- 

 moecia in a large drop of gelatine solution upon a slide, 

 cover and study the action of the cilia. The movements are 

 restrained more or less by the gelatine, and, with proper 

 lighting, should be easily observed. 



8. In a quiescent but living specimen observe the large 

 vacuole near either end of the body . Watch it long enough 

 to observe its contraction and disappearance, and the 

 formation of the circle of radiating clefts through the sur- 

 rounding protoplasm. Consider the part such movements 

 may play in keeping the contents of the cell in circulation. 



9. Observe also the nuclei nearer the centre of the body. 

 The nucleus is differentiated into two parts ; a large oval or 



