In the living Cephalodiscus a zooid can crawl by means of its proboscis over the gelatinous processes of the outer side of the coenoecium, a position which it can assume owing to the very great extensibility of the stalk, the proximal suctorial end of which remains attached to the inner surface of some part of the coenoecium (Andersson, 1907).
The simple form of ocellus described in the foregoing paragraph may become folded into a pit or cup, the interior of which becomes filled with a clear gelatinous secretion forming a sort of vitreous Modified after Linko, Travaux Soc. Imp. Nat., St.
E, Wandering endoderm cells of the gelatinous substance.
The spadix forms a gelatinous cyst, the so-called acrocyst (ac), external to the gonotheca (gth), enclosing and protecting the embryos.
In Limnocodium the body secretes a gelatinous mucus to which adhere particles of mud, &c., forming a protective covering.