The theory that the medusa is simply an organ, which has become detached and has acquired a certain degree of independence, like the well-known instance of the hectocotyle of the cuttle-fish.
Except in a few aberrant types, which are mentioned below, the mouth is surrounded by a much developed lip like a funnel directed downwards, and is armed with a horny beak not unlike that of a cuttle-fish.
Large salt-works are carried on in the vicinity, and thousands of fishermen are engaged, mainly between April and July, in catching cuttle-fish.
The apical end of the rotifer usually narrows suddenly beyond the curve of the gut and the cloacal aperture to form the foot of pseudopodium which ends in an organ of attachment, a pair of movable toes, each with the opening of a cement-gland (gl) at its tip. Thus for orientation we place the rotifer like the cuttle-fish, head downwards: the ciliated disk is basal or oral, proximal to the rest of the animal, the foot is apical, and the brain and cloacal aperture are anterodorsal.