42 STRUCTURAL AND SYSTEMATIC ZOOLOGY 



symmetry ; the head ; the absence of a neck ; the body 

 and scales ; the position and structure of the fins ; the 

 shape and structure of the mouth ; the teeth ; nostrils ; 

 tongue ; gills ; the lateral line ; microscopic structure of 

 scales and gills (Figs. 119, 320). 



Dissect away the skin ' from one side and study the 

 arrangement of the muscles. 



Cut open a specimen and study the position and 

 relation of the internal organs ; the peritoneum ; the 

 digestive (Fig. 246), circulatory, and reproductive systems 

 (Figs. 268, 269, 272); the structure of the heart; open 

 the skull and examine the brain and the principal nerves 

 arising from it (Fig. 336). Remove, by boiling, the flesh 

 from the skeleton, and study the structure of the latter 

 (Fig. 309). 



Make a microscopic examination of the blood 

 (Fig. 262). 



Obtain (from one of the state hatcheries, if necessary) 

 a series of living eggs and embryos, and study the de- 

 velopment of the fish. 



If opportunity offers, a fish market may be visited 

 and an examination made of the various kinds of food 

 fishes. 



Frog 



Vivarium and Aquarium Study. Keep live speci- 

 mens in aquarium jars or in boxes containing damp 

 moss. Study the manner in which the frog creeps, 

 leaps, swims, breathes, moves, and closes its eyes, 

 catches flies ; the position of the body at rest ; with a 

 thermometer try to get the natural temperature of the 

 body. 



Structure. In a recently killed specimen note the 

 color and structure of the skin, the position of eyes, 

 ears, nostrils, lips, the position and arrangement of the 

 lips and the teeth, the shape and mode of attachment of 



