Of the cell-wall (which is secreted by the living cell-body) the protoplasm dies, and a tissue in which this has occurred consists solely of the dead framework of cell-walls, enclosing in the cavities, originally occupied by the protoplasm, simply water or air.
In all cases, while the internal threads which bear the cortical branches consist of elongated cells with few chromatophores, and no doubt serve mainly for conduction of food substances, the superficial cells of the branches themselves are packed with chromatophores and form the chief assimilating tissue of the plant.
In the polyp the nervous tissue is always in the form of a scattered plexus, never concentrated to form a definite nervous system as in the medusa.
The adult worm, which is of extremely minute size, the male being only Fi l sth and the female s of an inch in length inhabits the alimentary canal of man and many other carnivorous mammalia; the young bore their way into the tissues and become encysted in the muscles - within the muscle-bundles according to Leuckart, but in the connective tissue between them according to Chatin and others.
Such a system is called a tissuesystem, the word tissue being employed for any collection of cells with common structural, developmental, or functional characters to which it may be conveniently applied.