18 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



ectosarc, while the more gradual extension is due to the 

 elasticity of the cuticle. 



X. Make a sketch showing as many of these points as 

 possible. 



XI. The Digestive Organs. 



The solid particles of food are taken directly into the 

 endosarc, as the}^ are in Paramcecium and Amoeba ; but the 

 apparatus for the ingestion of food is quite complicated. 

 It can be examined to the best advantage in specimens 

 which have been fed with finely-powdered carmine or in- 

 digo. In such a specimen notice : — 



a. The currents produced by the cilia of the peristome 

 and disc. These cilia act in such a way as to drive some 

 of the particles into the vestibule. 



h. When the vestibule becomes filled with the colored 

 particles, it is seen to be continuous with a horizontal 

 tube, the oesophagus (Fig. 4, e), which runs under the 

 disc into the endosarc. 



1. Notice that the walls of the oesophagus are covered 

 with small cilia, which keep the particles in motion, and 

 tend to drive them towards the inner end. 



2. Notice that some of the particles are drawn out of 

 the vestibule and thrown away from the body, and a vio- 

 lent contraction of the peristome and disc occasionally 

 drives all the particles out of the oesophagus. 



3. In very favorable specimens, the oesophagus and 

 vestibule may be seen to be lined by a continuation of the 

 cuticle. 



4. At the inner end of the oesophagus is a small, slightly 

 dilated crojp, which is also ciliated and lined by the cu- 

 ticle. 



5. As the particles of food are drawn from the oesopha- 

 gus into the crop, the cilia of the crop give them a whirl- 



