The coils and branches of the tube are packed by connective tissue and blood spaces.
It can then at the same time be observed, too, that the compact mass of connective tissue (" reticulum," Barrois) which lies between the muscular bodywall and the intestine is directly continuous with that in which the muscular layers are embedded.
The omnipresence of this connective tissue tends to exclude the formation of any perivisceral body cavity in Nemertines.
In Polia the connective tissue enclosed in the external muscular layer is eminently vacuolar - all the intermediate stages between such cells in which the vacuole predominates and the nucleus is peripheral and those in which the granular protoplasm still entirely fills them being moreover present.
The entosternite was probably in origin part of the fibrous connective tissue lying close to the integument of the sternal surface - giving attachment to muscles corresponding more or less to those at present attached to it.