出现期 meaning in English

patency
patent period

The testis development stages are determined according to cell ' s morphological characteristics , its size and number and the varying extent of chromatic agglutination . the development of testis may be divided into five stages : ( 1 ) multiplication of spermatogonium ; ( 2 ) growth of spermatocytes ; ( 3 ) maturation of spermatocytes : ( 4 ) initial appearance of spermatozoa ; ( 5 ) complete maturation of spermatozoa ? the reproductive seasons cover from march to april
可根据各期细胞大小、数量多少、核染色质凝聚程度等将精巢的发育时期划分为精原细胞增殖期、精母细胞生长期、精母细胞成熟期、精子开始出现期、精子完全成熟期共5个时期。