Deanesly R
Cell Tissue Res. 1977 Dec 19;185(3):361-71. doi: 10.1007/BF00220296.
During the 340 day pregnancy of the horse, the germ cells in the fetal ovary showed a meiotic prophase which began in days 60-70 and might be prolonged after day 200. Three or four successive oogonial mitotic proliferations passed into the meiotic prophase but the great majority of the oocytes first involved degenerated, and no appreciable numbers of primordial follicles were left behind. At 150 days of pregnancy and again at 197 days, oocytes in early meiotic stages filled the ovarian cortex. Primordial follicles were present, but rare. As the prophase gradually came to an end, groups of oocytes became enclosed by small 'boundary' cells which formed in the stroma. Coalescence of these groups led to the appearance of coiled and branching formations containing small and large oocytes. Many of the original groups, however, contracted and became narrow strands and these persisted until the end of pregnancy, many oocytes disappearing from them, while others eventually developed in primordial follicles.
在马340天的孕期中，胎儿卵巢中的生殖细胞呈现减数分裂前期，始于第60 - 70天，在第200天后可能会延长。三到四次连续的卵原细胞有丝分裂增殖进入减数分裂前期，但最初涉及的绝大多数卵母细胞退化，没有留下可观数量的原始卵泡。在妊娠150天时以及再次在197天时，处于减数分裂早期阶段的卵母细胞充满卵巢皮质。存在原始卵泡，但很罕见。随着前期逐渐结束，成群的卵母细胞被在基质中形成的小“边界”细胞包围。这些群体的合并导致出现包含大小不等卵母细胞的盘绕和分支结构。然而，许多原始群体收缩并变成狭窄的条索，这些条索一直持续到妊娠末期，许多卵母细胞从中消失，而其他一些最终发育成原始卵泡。
