278 PRACTICAL DIRECTIONS CHAP. 



2. The active movements, due to the cilia covering the 

 body. 



3. The marked distinction between cortex and medulla. 



4. The characters of the elastic cortex : (a) the super- 

 ficial cuticle, and deeper striated layer ; (b) the cilia arising 

 from the deeper layer, and projecting through the cuticle ; 

 (c) the trichocysts small oval sacs, imbedded in the deeper 

 layer ; (d) the two spherical contractile vacuoles, in close 

 relation with the deeper layer on the dorsal side : note that 

 canals radiate from them when they contract ; (e) the cilia 

 lining the buccal groove. (The potential anus behind the 

 mouth can only be seen at the moment of defaecation.) 

 Compare the mode of feeding with that of Amoeba. 



5. The characters of the medulla : (a) the food-vacuoles 

 and their circulation ; (b) the meganucleus and micronucleus , 

 which can be better seen when stained. Sketch. 



6. Add methyl -green or magenta. Then note again the 

 structure of cortex and medulla, as well as (a) the oval 

 meganucleus, near the middle of the body ; (b) the micronu- 

 cleus, a smaller body, close to the meganucleus ; (c) the 

 extruded trichocysts. Sketch. 



7. Look out for specimens undergoing transverse fission, 

 and also for others in process of conjugation. Sketch. 



Permanent preparations may be made as directed in the 

 case of Amoeba (p. 239). 



Vorticella. Mount some specimens in a drop of water, 

 and examine with the low power. The Vorticella will be 

 seen to have the form, of a wine-glass or bell with a long stem. 

 The stem frequently contracts spirally, the edge of the bell 

 being at the same time turned in, so as to give the animal 

 a rounded form. Put on the high power and note 



1. The form of the bell, its thickened rim or peristome, and 

 the disc, which forms a cover to the bell. 



2. The mouth and gullet, opening on one side between the 

 peristome and disc, which is here slightly raised. (The anal 

 spot is in the oral depression, but can only be seen at the 

 moment of defaecation.) 



3. The single row of cilia round the peristome and extend- 

 ing down the gullet on the one hand, and on to the raised 

 portion of the disc on the other. Run in a little finely 

 powdered indigo or carmine under the cover-glass, and note 

 the currents produced by the cilia : the granules of pigment 

 will be carried down the gullet. 



4. The contractions of the bell and stalk. 



