9. (a) Explain what is meant by the term "central nervous system." (b) Describe the tissue elements which enter into its composition. (c) Explain, as far as you can, the function of each structure described. (d) How is the central nervous system developed in the frog, and (e) in the rabbit? (f) What conclusions may be drawn from the facts stated as to the origin of the central nervous system in evolution? 10. Give an account of the structure (including histology) and of the functions of the spinal cord and spinal nerves of the frog. 11. Give a description of the minute structure and chemical characters of the following tissues as seen in the frog:-- cartilage, bone, muscle. From which of the primary cell-layers of the embryo are they respectively developed? 12. What substance is excreted by the renal organ of a frog, and what relation does this substance bear to the general life of the organism? Describe the parts by which similar excretion is believed to be effected in amoeba, hydra, earthworm, mussel, and lobster. 13. Describe, with illustrative sketches, the structure of the connective tissue, cartilage, and muscular tissue of a frog. Also describe the structure of the muscular tissue of the lobster and snail. 14. Give in account of the more important features in the development of the frog. 15. Describe and compare the structure of the renal organs in a frog and a rabbit. 16. Give an account of the structure of the genito-urinary organs of the frog. Compare these organs of the frog with those of the dog-fish and of the rabbit. Distinguish in each case the conditions of the two sexes, and describe briefly the microscopic structure and development of the ova and of the spermatozoa. 17. Describe, with diagrams, the arrangement of the urinary and generative organs in the male of (a) the rabbit, (b) the dog-fish, and (c) the frog; (d) point out the most important differences between them. 18. (a) Describe the structure of the ovarian egg of the rabbit, (b) and of the pigeon, (c) and of the frog; (d) from what part of the embryo do they originate? (e) What is the structure and origin of the ovarian follicle in the rabbit, and (f) of the ovarian stroma? (g) What is the "granulosa" and what the "zona pellucida"? 19. Describe the pre-segmentation changes, mode of impregnation, and early stages of development in the ovum of the frog, as far as the closure of the neural canal. 20. Illustrate, with diagrams, from the structure of typical organisms, the principle of repetition of similar parts. -Note on Making Comparisons_