CHAPTER XIX 



CHORDATA (CONT.): SUB-PHYLUM VERTEBRATA (FISHES, AMPHIBIANS, 

 REPTILES, BIRDS, AND MAMMALS) 



LABORATORY EXERCISES 



For general illustration of the vertebrates the author is 

 convinced that no form is superior to the frog for use in ele- 

 mentary classes, although some teachers prefer a fish. In 

 a course arranged for one year it is not desirable to make 

 elaborate dissections of more than one or two vertebrate types. 

 Directions are given both for the fish and the frog for the con- 

 venience of those teachers who prefer the former. Supplemen- 

 tary studies for the other classes of vertebrates will be found 

 in connection with the chapters devoted thereto. 



341. Fish. Any common fish will serve perch, sucker, trout, smelt. Speci- 

 mens eight to ten inches in length are of most suitable size. If convenient one- 

 half the class might take one species and the remainder another. 



A. The Living Animal. Place in a tub of water, or better in a vessel one side 

 of which is glass. Watch the locomotion and notice all the accompanying motions 

 of the various parts. What is the rate of the tail stroke? How far, on an average, 

 does one stroke of the tail carry the fish? Compare these points when the fish is 

 in very rapid motion. What part do the anterior fins play in locomotion? Bind 

 one of them flat against the body with a string. Bind both. Results? Experi- 

 ment similarly with the other fins and see if your first conclusions are strengthened. 

 Do you find any variations in the above respects by comparing several species? 



How does the temperature of the fish compare with that of the water? Allow 

 one specimen to remain for an hour or more in water at a temperature of 70 F. ; 

 another in cooler water (50 F.): compare results. 



Can the fish detect in the water the presence of substances which have a decided 

 taste to us? Use colorless solutions, acid, sugar, quinine. Can you get the 

 animal to show any choice as to food? - 



Note the motions of mouth and eyes. Can the fish see any point with both 

 eyes at once? 



B. External Anatomy. (Make careful outline sketches showing all points of 

 structure.) 



The Topography of the Body. Note the symmetry; indicate the degree of 

 differentiation of anterior and posterior ends, and of dorsal and ventral surfaces, 

 as shown by the shape, special organs, etc. What structures appear paired? 

 To what degree are head, trunk, and tail clearly distinguishable? Locate and 



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