Mask. — Lepidosteus. 



ABBREVIATIONS. 



cap. Head of villus. pd. Stalk of villus. 



c.-t. cp. Connective-tissue corpuscle. rx. Root of villus. 



fus. mat. Maturation spindle. st. vil. Villous layer of egg membrane. 



gran. Granulosa. tk.fol. Membrana propria of thecafolliculi. 



m ]>y. can. Micropylar canal. vac. Vacuole. 



m py. ci. Micropylar cell. vit. Vitellus. 



nl. Nucleus. vs. g. Germinative vesicle. 



nl. gran. Nucleus of granulosa cell. z. r. Zona radiata. 



PLATE I. 



All the figures of this plate were made from material that had not been hardened, 

 and all the figures except Figs. 7 and 11 are magnified 472 diameters. 



Fig. 1. A surface view of a small portion of the villous layer of egg membrane. 



" 2. The appearance presented by the same layer when the region near the 

 boundary between it and the zona radiata is in focus. Some of the 

 roots of the villi are seen between the stalks. 



" 3. The zona radiata when the focusing is a little below its outer surface. 

 A few pore-canals are occupied by roots of villi and appear darker. 



" 4. A portion of a radial section after being treated with weak hydrochloric 

 acid. Two of the villi much more elongated than the others. 



" 5. A radial section of a fresh egg-shell, showing the relative thickness of 

 the zona radiata and the villous layer. 



" 6. A portion of the same with the villous layer removed, but leaving its 

 roots in the spiral pore-canals. Examined in glycerine. 



" 7. Portions of the villous layer removed from the zona radiata and much 

 swollen in water. The roots appear like a fine fringe. X 145. 



" 8. The appearance of the pore-canals after treatment with hydrochloric acid. 

 The most of them, especially toward the margin of the figure, should 

 have been drawn larger but faint. A few are conspicuous from the 

 presence of roots of villi. 



" 9. a to // and j to n, isolated villi in various stages of elongation after imbi- 

 bition of very dilute hydrochloric acid ; i, after soaking in water 

 only. 



" 10. A fragment of the zona radiata deprived of the villous layer and treated 

 with weak hydrochloric acid until all the pore-canals except those 

 containing villous roots had disappeared. The zona, having become 

 soft, was partly crushed, so that the roots were seen obliquely, the 

 ends toward the top of the plate being the ones torn from the stalk. 



" 11. Optical radial section of the micropylar region of a fresh egg, the wall of 

 the membrane beyond the micropyle being projected on the same 

 plane. X 145. 



" 1 1". Optical cross-section of the same, at plane a of Fig. 11. 



" 11''. Optical cross-section of the same at plane b of Fig. 11. 



