其腹面口区具二环围口纤毛列；背面具一列背刚毛。
There are two circumoral ciliary rows on the buccal region and a dorsal row of bristles.
原胚初期胚体出现背腹极性，腹面的细胞小，细胞质稠密，液泡较少；
During early proembryo stage, the dorsiventrality appears in the proper of the embryo. On the ventral side, the cells are small with dense cytoplasm and few vacuoles.
其腹面口区具二环围口纤毛列及一口前纤毛列；背面具一列背刚毛；腹面纤毛列的数目可发生较大变动。
There are two circumoral ciliarvrows and a preoral ciliary row on the buccal region and a dorsal row of bristles.
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