Sections of Vipera albicornuta ovary (H × E). (a) Stage I follicle (primary follicle): the former is <5 mm in length. No deutoplasmic granules were found in the ooplasm. The granulose contained pyriform, intermediate and small cells. (b) Stage II follicle: 5–15 mm in length. Deutoplasmic granules started to form and 2-3 layers of small cells existed in the granulose. (c) Stage III follicle: 15–25 mm in the length. The number and size of deutoplasmic granules increased, but there was only one layer of follicular cells. D: deutoplasmic granules; I: intermediate cell; O: ooplasm; P: pyriform cell; S: small cell. Scale bars = 25 μm.