Thus the Galeolaria lutea has two kinds of polypites, both nutritive, but one is sterile, the other prolific. The latter are similar to the prolific individuals of the syncorine Hydræ, in which the anterior part is a digestive organ, while on the base or stalk true medusa-zooids are found. It is curious that the spathe-protecting plate of the Galeolaria appears in the egg as a globe of such size that the other parts seem to be merely the appendages.
Fig. 119, p. 108.
APOLEMIA CONTORTA.
The Apolemia contorta ([fig. 119]) unites the most graceful form to the utmost transparency and delicacy of tissue. It has a double float, the first small and globular, the second long and oval. The neck is short, the rose-coloured body is flat as a ribbon, and covered with thin, curved, pointed, and imbricated plates, like tiles on the roof of a house, but so minute that they are only perceptible to the naked eye by a slight iridescence. At the extremity of the short neck buds, semi-developed buds, and perfect swimming cups are arranged in vertical series; and as the flat body is twisted into a spiral to its farthest end, the cluster of bells forms a perfect cone with the float at its apex. The bells are flattened; and there is always in their more solid posterior part a single canal rising directly from the general trunk which divides into four branches; and these, having traversed the swimming cavity, unite anew in a circular canal, or iris, destined to shut and open the cup.
Fig. 120, p. 109.
PHYSOPHORA HYDROSTATICA.
The sterile polypites that are attached at intervals by their hollow stems to the twisted body of the Apolemia, have twelve rows of cells inserted in the bright lining of their digestive cavities; their anterior part has a trumpet-shaped mouth full of thread-cells. The tentacles affixed to their stems and their secondary lines are like those of the Diphyidæ. Besides these sterile polypites, which serve only to feed the animal, the Apolemia has a kind of mouthless prolific organs, which do not contribute to the general nourishment: each group has a pair of them attached to the extremity of a branching stem. They resemble polypites in being long and contractile at their extremities; the interior is full of a substance like sarcode, and encompassed by a red ring. Female buds yielding eggs appear on the stem of one of these organs, while male buds are developed into medusiform zooids on the stem of the other, which become detached, swim away, and the fertilized eggs yield young Apolemiæ.
The natural position of an individual of the family of the Physophoridæ when at rest is to hang perpendicularly from its air-vessel. The body, which begins with a pyriform float, descends in a slender filiform scarlet tube with a number of hyaline natatory cups or bells attached on each side. The lower end of the body enlarges into a bulb or disk supporting various appendages.