PRACTICAL ZOOLOGY 41 



hardened in formalin or alcohol and study the supra- 

 branchial canal, gills, etc. (Fig. 275). 

 Examine the gills for eggs and young. 



Land or Water Snail 



Field or Aquarium Study. -Study its movements ; its 

 mode of respiration; its feeding; the movements of the 

 " rasp " ; the use of the " feelers " ; the manner in which 

 the body is protruded from the shell and retracted. 



Structure. Compare its shell with that of the 

 mussel. Note the whorls ; the lines of growth ; the 

 attachment of the body to the shell (Fig. 297). 



Remove the soft parts and study their structure, 

 the digestive system (Fig. 227); the large liver; the 

 heart, the brain, and nervous system (Figs. 243, 331, 

 351). Note that the bodies of both these mollusks 

 are unsegmented and are without appendages. 



Snails kept in aquariums frequently attach their eggs 

 to the sides of the jar or to water plants. The seg- 

 mentation of the egg and the development of the larva 

 may be studied with a low power or with a hand lens. 



VERTEBRATES 



Vertebrata 



Fish 



Aquarium Study. Study living specimens in the 

 aquarium, their movements of locomotion and of the 

 various fins ; mouth, gill covers, and gills ; the eyes ; 

 the method of feeding and of respiration ; the distribu- 

 tion of colored spots on the body ; the adaptation of 

 shape to locomotion in the water ; test the use of each 

 fin by binding them separately to the body by means of 

 rubber bands slipped on over the fish's head. 



Structure. On a dead specimen note the bilateral 



