† protospongianadj. [ < proto-comb. form + classical Latin spongia (see spongen.1) + -ansuffix, after German Protospongia ( Haeckel Kalkschwämme (1872) I. 338)] ZoologyObsoleterare (in Haeckel's terminology) designating an early stage in the development of a sponge.
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1884 A. Hyatt in Proc. Boston Soc. Nat. Hist.23 86 We have not been able to separate the Protospongian stage of Haeckel from the ascula.