What is the relationship between germinal layers and the formation of the body cavity in the case of coelomates,acoelomates,and pseudocoelomates?

(N/A) $\rightarrow$ All adult multicellular organisms typically possess a concentric arrangement of tissues in the body. These tissues are derived from embryonic cell layers called germinal layers.
$(i)$ Coelomate: These organisms possess three germinal layers: ectoderm,mesoderm,and endoderm. The body cavity (coelom) is lined by the mesoderm on all sides,resulting in a true coelom.
$(ii)$ Acoelomate: These organisms possess three germinal layers (ectoderm,mesoderm,and endoderm),but the body cavity is completely absent because the space between the body wall and the digestive tract is filled with parenchyma or mesoderm.
$(iii)$ Pseudocoelomate: These organisms possess three germinal layers (ectoderm,mesoderm,and endoderm). However,the mesoderm is present as scattered pouches between the ectoderm and endoderm,and it does not line the body cavity,hence a true coelom is absent.
$\rightarrow$ Examples:
$(i)$ Coelomates: Phylum $Annelida$,$Mollusca$,$Arthropoda$,$Echinodermata$,$Hemichordata$,and $Chordata$.
$(ii)$ Acoelomate: e.g.,$Platyhelminthes$.
$(iii)$ Pseudocoelomate: e.g.,$Ascaris$ (Phylum $Aschelminthes$).