The coenosarc may consist of a single elongated tube or stolon, forming the stem or axis of the cormus on which, usually, the appendages are arranged in groups termed cormidia; or it may take the form of a compact mass of ramifying, anastomosing tubes, in which case the cormus as a whole has a compact form and cormidia are not distinguishable.
In forms with a compact coenosarc such as Velella, Physalia, &c., the separate cormidia cannot be sharply distinguished, and such a condition is described technically as one with " scattered " cormidia.
In forms in which, on the other hand, the coenosarc forms an elongated, tubular axis or stem, the appendages are arranged as regularly recurrent cormidia along it, and the cormidia are then said to be " ordinate."
The following are some of the forms Cuvier, Lankester's Treatise on of cormidia that occur: Zoology.
Two sections can be distinguished, the Rhizophysina, with long tubular coenosarc-bearing ordinate cormidia, and Physalina, with compact coenosarc-bearing scattered cormidia.