Mature eggs during fertilization.

A. The metaphase II plate is located at the animal pole of the egg (arrowhead); AB-PAS-AH stain. B. The first polar body (arrowhead) that appeared in the space between the oolemma and edge of the jelly coat (jc). The segregated ooplasm (sg) is seen. AB-AHE stain. C. A general view of the animal pole during fertilization. The first polar body (arrowhead), the male pronucleus (mp), the female pronucleus (fp), the space (sp) between the oolemma and the edge of the jelly coat and the segregated ooplasm are seen. PAS-AB-AH stain. D. A higher magnification of the animal pole shown in ‘C’. The polar body (pb) is clearly seen in a state of division. E,F. The formation of two (E) and three polar bodies (F). The male pronucleus (arrowhead) is located in the peripheral zone of the egg (the coarse-grained yolk area) and the segregated ooplasm (in ‘E’) are clearly visible. AB-PAS-AH stain. G. Eggs located within the jelly coat. The ooplasmatic segregation is clearly visible. Inside the jelly coat are nematosomes (ns). AB-AHE stain. H. Numerous spermatozoa (sz) and one nematosome are seen inside the jelly coat. AHE stain. I. Some sperm heads (hs) are seen inside the eggs. They are visible as dark spots. AHE stain. J.K. The edge of the cortical layer (arrowheads) at the animal pole is characterized by a rough view. Fine granules are seen in the space between the oolemma and the internal edge of the jelly coat. In ‘J’ the female pronucleus is clearly seen, in ‘K’ the polar body is depicted. L. The edge of the cortical layer at the vegetative pole of the same egg is smooth (arrowhead). AB-AHE stain. cl, cortical layer; fp, female pronucleus; hs, sperm heads; jc, jelly coat; mp, male pronucleus; ns, nematosome; pb, polar body; sg, segregated ooplasm; sp, space between the oolemma and the edge of the jelly coat; sz, spermatozoa. Arrowhead in A shows metaphase II plate; arrowheads in B and C show the polar bodies; arrowheads in E and F show male pronuclei; yellow arrowheads in J and K illustrate a rough view of the cortical layer edge at animal pole and arrowhead in L shows a smooth view of the cortical layer at the vegetative pole in the same egg. Scale bars = 20 μm.