6. On the vertebræ notice any irregularities, prominences, or roughenings. For what are such bones better adapted than smooth bones would be? 7. How is the frog's humping permitted? How are the urostyle and the pelvis connected, if at all? Has this any effect on motion? (See living frog.) 8. In parallel columns, keeping corresponding parts in a line, tabulate the bones of the fore and hind limbs. 9. State how extra length has been attained in the hind leg, and give the purpose or the result of this lengthening. 10. In the forearm notice the fusing of the radius and ulna. How would these parts act in rotating the hand, as compared with your own, where they are free? Compare also the tibia and fibula. Where in the frog's leg is turning made possible by the use of parallel bones? 11. Compare the frog's hand and foot as to number of fingers and toes; as to length and spread. Have any fingers or toes only two phalanges? 12. How would an inner skeleton affect the growth and the size of an animal, as compared with an outer skeleton, like the clam's? 13. How would the lack of an outer skeleton influence sensitiveness, activity, and intelligence? _Suggested drawings._ a. The skull and trunk, with appendages of one side. b. Each set of bones separately, as the skull, the column, etc. Comparative Study of Amphibia _Materials._ Various amphibia, either dead or alive, such as newts, mud puppies (_necturus_), salamanders, and several species of frogs and toads, especially tree toads. _Observations._ Answer the following questions with respect to each animal:-- 1. What regions of the body are present? What is the general shape and size of the body? 2. For what kind of locomotion are the limbs fitted? How? 3. Have the hands and feet any special adaptations? If so, what are they and for what purpose? 4. With what organs does the animal breathe? If with gills, are they external or internal? 5. Judging from the specimen, what do you think is the habitat? Give reason for your answer. Summary from the Comparative Study of Amphibia 1. Which of the amphibia in this study are fish-like in character? What are the fish-like characters? Do you think these fish-like amphibia are of a lower or higher type than the others? Give reasons for your answer. 2. Show how the variation in (a) the form of the body, (b) color patterns, and (c) the structure of the legs and arms of the amphibia are related to habitat and mode of life. Amphibia: A General Review and Library Exercise 1. The usefulness of the American toad. 2. The breeding habits of the common frog; of the Surinam toad; of the obstetrical toad; of the "smith." 3. The development of the axolotl. 4. The habits of the tree frogs and their variable coloration. 5. The croaking of frogs and of toads. 6. The flying frog of Ceylon. 7. The distribution and habits of the hellbender; of the mud puppy; of the Congo "snake."