van den Biggelaar J A
J Morphol. 1977 Oct;154(1):157-86. doi: 10.1002/jmor.1051540111.
In Patella vulgata the 32-cell stage represents a pause in the mitotic activity prior to the differentiation of the mesentoblasts mother cell 3D. At the onset of this stage, the embryo is radially symmetrical. Nevertheless, the plane of bilateral symmetry is indicated as it passes through the macromeres forming the vegetal cross-furrow. From the early beginning of the 32-cell stage, all four macromeres introdude far into the interior and tough the centrally radiating cells of the first quartet of micromeres. The two cross-furrow forming macromeres (3B and 3D) intrude the farthest and come into contact with the greatest number of micromeres. Finally, the contacts are extended significantly and maintained with only one of these macromeres. From that moment, this cell can be called the macromere 3D and the dorsoventral axis is determined. The evolution of the internal cell contacts between the micromeres of the first quartet and the macromeres indicates an essential role of the former in the determination of one of the latter as the masentoblasts mother cell, and thus in the determination of dorsoventral polarity.
在普通滨螺中，32细胞期代表中胚层母细胞3D分化之前有丝分裂活动的一个停顿。在这个阶段开始时，胚胎呈辐射对称。然而，双侧对称平面是通过形成植物性横沟的大卵裂球来指示的。从32细胞期开始时起，所有四个大卵裂球都深入到内部，并与第一组小卵裂球的中央辐射细胞接触。形成两条横沟的两个大卵裂球（3B和3D）侵入得最远，与最多数量的小卵裂球接触。最后，接触显著扩展并仅与其中一个大卵裂球保持接触。从那一刻起，这个细胞就可以被称为大卵裂球3D，背腹轴就确定了。第一组小卵裂球和大卵裂球之间内部细胞接触的演变表明，前者在将后者中的一个确定为中胚层母细胞方面起着重要作用，从而在背腹极性的确定中也起着重要作用。
