The Frog — An Amphibious Vertebrate Animal 441 



dular cells of the oviduct. There are no copulatory organs. A yellowish, 

 hand-shaped organ, known as the fat body, is located in front of each 

 reproductive organ for the storage of food. There are no amnion and 

 no allantois attached to the developing embryo as in reptiles and mam- 

 mals. The embryology of the frog is considered in a special chapter. 



QUESTIONS AND TOPICS 



1. List the characteristics which place the frog in the phylum Chordata, sub- 

 phylum Vertebrata, and class Amphibia. 



2. Explain and give the significance of (1) protective coloration, (2) internal 

 bony skeleton, (3) closed system of arteries, veins, and capillaries, (4) lymph, 

 (5) lymph hearts, (6) three-chambered heart, (7) paired appendages with 

 digits, (8) well-developed skeletal muscles which function in opposition, (9) 

 erythrocytes which contain hemoglobin, and (10) special cells to assist in the 

 clotting of blood. 



3. Describe the structure and functions of the following for the frog: (1) in- 

 tegument, (2) motion and locomotion, (3) ingestion and digestion, (4) circu- 

 lation, (5) respiration, (6) excretion, (7) coordination and sensory equip- 

 ment, and (8) reproduction. In what specific ways have these shown im- 

 provements over the same in lower types of animals? 



4. Explain (1) the origin and insertion of a muscle, (2) pectoral and pelvic 

 girdles, (3) auricle and ventricle, (4) vasa efferentia and ureter, and (5) 

 ureter and oviduct. 



5. Describe the structure and functions of the various parts of the digestive 

 system, including the physiology of digestion in detail. 



6. Discuss the advantages of a three-chambered heart over a two-chambered one. 



7. Explain how blood is carried to and from the lungs and skin. 



8. Describe the blood of the frog, including advantages over blood of animals 

 studied previously. 



9. Explain how the circulatory system must be changed when a system of respi- 

 ration (lungs and skin) is present. 



10. Explain how the circulatory system must be developed when only one pair of 

 kidneys excrete wastes. 



11. Discuss the improvements in structure^ and functions of the nervous system 

 and sensory equipment of the frog over animals studied previously. 



12. List the number, names, origin, distribution, and functions of the ten pairs of 

 cranial nerves in amphibia. In what ways do reptiles, birds, and mammals 

 differ from amphibia and fishes in regard to cranial nerves? 



13. List the conclusions you can draw from your studies of the frog. 



SELECTED REFERENCES 



Dickerson: The Frog Book, Doubleday, Page & Co. 



Holmes: The Biology of the Frog, The Macmillan Co. 



Kingsley: The Frog (Guide for Dissection), Henry Holt & Co., Inc. 



Marshall: The Frog, The Macmillan Co. 



Noble: Biology of the Amphibia, McGraw-Hill Book Co., Inc. 



Shumway: The Frog (Laboratory Guide), The Macmillan Go. 



Stuart: Anatomy of the Bullfrog (Laboratory Guide), Denoyer-Geppert Co. 



