PLATE II {co>itl,nie(l). 



Tig. 

 8. — Nictitating menibrane. Magnifyiug power, Hartuack's eyepiece No. 3, 

 objective No. 10, immersiou. 



a. Pigment-cells in the superficial layer of the anterior surface. 



b. Nucleus. 



c. Varicosities of the process. 



d. Larger pignieut-granules. 



PLATE III. 



9_ — Nictitating membrane. Magnifying power, Hartnack's eyepiece No. 4, 

 objective No. 10, immersion. 



a. Pigment-cells of the middle layer of the nictitating membrane. 



b. Nucleus. c. Nucleolus. 



d. Processes. 



e. An ordinary branched cell. 



10. — Nictitating membrane. Magnifying power, Hartnack's eyepiece No. 4, 

 objective No. 8. 

 a and b. Subepithelial non-medullated nerve-fibres. 



c. Finest nerve-fibres between the deepest epithelial cells. 



d. The deepest epithelial cells. 



14. — A capillary vessel of the mesentery of the frog. 

 a. The vessel with blood-corpuscles. 

 Aandc. Non-medullated nerve-fibres. 



PLATE IV. 



11. — Mesentery of the frog. Magnifying power, Hartnack's eyepiece No. 3, 

 objective No. 8. 



a. A larger trunk of medullated nerve-fibres. 



b. A single medullated nerve-fibre, 

 cand d. Non-medullated nerve-fibres. 



e. An element belonging to the membrane. 



f. An intercalated nucleus of a fine nerve-fibre. 



g. A capillary vessel. 



12. — A, an artery; 13, a vein of the mesentery of the frog, showing the dis- 

 tribution of the fine non-medullated nerve-fibres in the adveutitia. 

 Magnifying power, Hartuack's eyepiece No. 3, objective No. 7. 



13. — Small vessels of the mesentery of the frog. Magnifying power, 

 Hartnack's eyepiece No. 9, objective No. 7. 



a. The vessel with blood-corpuscles. 



b, c, and d. Non-medullated nerve-fibres. 



