(3) Between these two layers gelatinous material Mesenchyme is there. (2) Inner Choanocytic layer or Choanoderm, Collar cell or Choanocytes (Flagellated) Schulze (1878), Butschli (1884), Sollas (1884) and Delage (1898) separated sponges from other metazoans on basis of embryological studies, and suggested a separate group, “Parazoa” for these. Robert Grant (1825) finally proved that sponges are animals, and coined the name ‘Porifera’ for these. Their body wall has numerous minute pores, called ostia, through which a continuous current of outside water is drawn into the body. The word “Porifera” means pore bearers (Gr., porus = pore ferre = to bear). ![]() Familiar as sponges, these animals are well-known for their ability to absorb and withhold fluids. Lowest multicellular animals or metazoans without true tissues, i.e., at “Cellular level” of body organization.
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