364 ELEMENTARY BIOLOGY. [CHAP. 



LABORATORY WORK. 



A. Examine duckweed roots, confervas, &c., with J inch 

 objective avoiding pressure ; having found a group of 

 Vorticella note the following points with a higher 

 power. 



i. In the extended state of the animal, 

 a. The body. 



a. Its size (measure). 



b. Form ; broadly speaking, that of an inverted 

 bell : note 



a. The prominent everted rim (peris tome). 



j3. The flattened central disc projecting above 



the peristome. 



y. The cilia fringing the disc. 

 8. The depression between the peristome and 



disc. 



e. The vestibulum ; a chamber in the hollow 

 between the peristome and disc. 



c. Structure. 



a. The thin, transparent, homogeneous external 



layer (cuticle), 

 ft. The granular layer (ectosare) inside the cuticle, 



longitudinally striate at the base of the bell 



(inyophan layer). 

 y. The central more fluid part (endosarc) not 



sharply marked off from /?. 



