The porifera and coelentera . cases it must be considered as a normal featiue of certainspecies (Evans, 1899). Union between the spicules is effected either by means offibrous tissue or by spongin.
Why are poriferans referred to as having a cellular grade of body construction despite being multicellular organisms? - Quora
Phylum - Porifera (Sponges)
Phylum Porifera - Sponges - ppt video online download
Porifera are multicellular, while they don't have tissue. Why? - Quora
Wounding response in Porifera (sponges) activates ancestral signaling cascades involved in animal healing, regeneration, and cancer | Scientific Reports
A muscle-related contractile tissue specified by MRTF-activity in Porifera | bioRxiv