Into the space between the walls of the coelom and the outer body-wall, originally filled with jelly, definite cells now wandered, chiefly derived from the coelomic walls.
In certain cases, however, the walls of the oesophagus appear to be very closely applied to the muscular body-wall and this vascular space thereby considerably reduced.
In the Coelomata, on the other hand, there is another cavity, dividing the body-wall into two layers: an internal layer surrounding the gut, and an external layer.
(h) The muscles of the body-wall and gut do not consist of transversely-striped muscular fibre, but of the unstriped tissue observed also in Chaetopoda.
T t, E), and at the same time the appendages appear as hollow processes of the body-wall, a mesoblastic somite being prolonged into each of them.
The blood fluid does not flow in any definite direction; its movements are largely influenced by those of the muscular body-wall.
The zooids of which the colonies of Ectoprocta are composed consist of two parts: the body-wall and the visceral mass (figs.
The visceral mass was accordingly termed the "polypide" and the body-wall which contains it the "zooecium."
The muscular tissue of the dorsal body-wall is much reduced and the integument here is thin and FIG.
D, A female with one half of the body-wall taken away to show the coiling generative organs.