90 ELEMENTARY BIOLOGY. [iX. 



and actively locomotive, and the former is particularly re- 

 markable for its relatively large size and semilunar contour, 

 and for the length and distinctness of its curved oesophagus. 

 Balantidium is pyriform, and has a very short oesophageal 

 depression. 



LABORATORY WORK. 



A. Examine duckweed roots, confervse, &c., with \ inch 

 objective avoiding pressure; having found a group of 

 Vorticellce note the following points with a higher 

 power. 



1. In the extended state of the animal. 



a. The hody. 



a. Its size (measure). 



h. Form ; broadly speaking, that of an inverted bell : 

 note — 



a. The prominent everted rim (peristome). 



/8. The flattened central disc projecting above the 

 peristome. 



7. The cilia fringing the disc. 



S. The depression between the peristome and disc. 



e. The mouth of the chamber {vestibulum) into 

 which the oesophagus and anus open, in the 

 hollow between the peristome and disc. 



c. Structure : — 

 a. The thin, transparent, homogeneous external 



layer [cuticle). 



