1. The dorsoventral polarity of Drosophila egg is established by means of signaling between the germ line-derived oocyte and the surrounding somatic follicle cells.
   果蝇胚胎的发育是由四种系统，分别控制头尾部、前部、后部以及背腹部的形成。
2. In the posterior segment, its dorsoventral axis was the longest, and could be divided into two parts: the dorsal and the ventral parts.
   后段的背腹径最长，可分为背侧部和腹侧部，两部分的细胞分界清晰。

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