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 a fish may be used. In a course 

 arranged for one year it is not desirable to ra'ake elaborate dis- 

 sections of more than one or two vertebrate types. Directions 

 are given both for the fish and the frog for the convenience of 

 those who prefer the former. Supplementary 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 and compare 

 results. 



A. The Living Animal. — Place in an aquarium. 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 fiat against the body 

 with a string. Bind both. Results? Experiment 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 w"hich 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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