I was reading about invertebrates, and noted that Ctenophores and Cnidarians have a gel-like, acellular layer separating their ecto and gastrodermis, termed the mesoglea. I know these two phyla are diploblastic, and that acoelomorphs, ecdysozoans, lophotrochozans, and deuterostomes (the bilaterians) are all triploblastic, thus they have three primary tissue layers during embryonic development (epi, endo, and mesoderm) as opposed to two. Is it plausible to hypothesize that perhaps the mesodermic layer of the bilaterians evolved from the mesoglea of our diploblastic ancestors? I know the mesoglea functions mainly in support, and read that the mesoderm gives rise to many cell types, including bone and muscle cells. I searched online for any articles examining the evolutionary relationship between the two, but couldn’t find anything. I’m kind of new to evolutionary bio, so sorry if this is way off the mark.