Each animal phylum has its own bauplan. The phylotypic stage is the ontogenetic stage during which the phylum level characteristics appear. This stage refers to different stages of development in different animals. Sponges are one of the simplest, and probably the oldest multicellular lineage of extant animals. On the basis of the analysis of sponge development during (i) sexual and asexual reproduction, (ii) regeneration from small body fragments, and (iii) cell reaggregation, we suggest a hypothetical variant of their phylotypic stage (spongotype): the mono-oscular juvenile—the rhagon. The major feature, which permits to consider the rhagon as the phylotypic stage of the Porifera is the final, definitive position of all the cellular and anatomical elements of the future adult sponge. It seems that at the rhagon stage the pattern of the axial complex of anlagen is already formed, and only growth processes occur at the later stages.

中文翻译：

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寻找 Porifera 的祖先组织和系统型阶段

每个动物门都有自己的 bauplan。系统发育阶段是个体发育阶段，在此期间门水平特征出现。这个阶段是指不同动物的不同发育阶段。海绵是现存动物中最简单，也可能是最古老的多细胞谱系之一。根据对 (i) 有性和无性繁殖、(ii) 小体碎片再生和 (iii) 细胞重新聚集过程中海绵发育的分析，我们建议其系统发育阶段（海绵型）的假设变体：小眼幼虫——犰狳。允许将ragon视为Porifera的系统发育阶段的主要特征是未来成年海绵的所有细胞和解剖学元素的最终确定位置。