58 PRACTICAL ZOOLOGY. 



Make a drawing, naming all the parts, of the snail-shell 

 with the aperture toward you; with the aperture away 

 from you ; with the apex toward you. 



Lay the snail-shell beside a common screw; if the 

 whorls turn like the threads of the screw, it is a right- 

 hand shell ; if they turn the other way, it is a left-hand 

 shell; the right-hand shells are sometimes called dextral, 

 and the left-hand, sinistral. 



Clams, snails, and oysters belong to the branch of the 

 animal kingdom called Mollusca; the clam is a bivalve; 

 the snail is a univalve. 



Read Morse's " First Book of Zoology," on snails and 

 clams. 



PARAMECIUM. 



In a tub, or aquarium, in which clams have been kept, 

 a thin white film may form on the surface of the water. 

 This is more likely to occur if some of the clams die and 

 the water gets " bad." Place on a slide a drop of this 

 water with some of the white film, with a piece of paper 

 under the edge of the cover to keep from crushing the 

 animalcules. Examine first with a low, then with a high 

 power of the microscope. 



Paramcecium is somewhat slipper-shaped, swimming 

 actively by means of vibrating, hair-like projections, or 

 cilia; are these of the same size on all parts of the body? 



Find, on one side of the body, a widely open, funnel- 

 shaped cavity, extending obliquely backward into the 

 body; this is the vestibule; the narrower, inner part of 

 this funnel-shaped cavity is the gullet, or esophagus; 



