Fig. 88. Colony of Coryne; natural size. (Agassiz.) Click on image to view larger size.
|  Fig. 90. Free Medusa of Coryne. (Agassiz.) |
Fig. 89. Magnified head of Coryne; a stem, t tentacles, o mouth, v body, d Medusa. (Agassiz.) Click on image to view larger size. |
Sarsia. (Coryne mirabilis Ag.)
Among the most common of our Tubularians is a small, mossy Hydroid (Fig. 88), covering the rocks between tides, in patches of several feet in diameter. [Fig. 89] represents a single head from this little mossy tuft greatly magnified, in which is seen the medusa bud arising from the stem by the process already described in the other Hydroids. In [Fig. 90] we have the little Jelly-fish in its adult condition, about the size of a small walnut, with a wide circular opening, through which passes the long proboscis, hanging from the under surface of the disk to a considerable distance below its margin. The four tentacles are of an immense length when compared to the size of the animal. As a general thing, the tentacles are less numerous in the Tubularian Medusæ than in those arising from other Hydroids; they want also the singular limestone concretions found at the base of the tentacles in the Campanularian Medusæ. In [Fig. 91] we have one of the Tubularian Medusæ (Turris vesicaria A. Ag.) which lifts a rather larger number of tentacles than is usual among these Jelly-fishes. We never find the tentacles multiplying almost indefinitely in them, as in Zygodactyla and Eucope. The little Jelly-fish described above is known as Sarsia, while its Hydroid is called Coryne. These names having been given to the separate phases of its existence before their connection was understood, and when they were supposed to represent two distinct animals. They are especially interesting with reference to the history of Hydroids in general, because they were among the first of these animals in whom the true relation between the different phases of their existence was discovered. Lesson named the Sarsia after the great Norwegian naturalist, Sars, to whom we owe so large a part of what is at present known respecting this curious subject of alternate generations.
Fig. 91. Turris vesicaria; natural size.
Bougainvillia. (Bougainvillia superciliaris Ag.)
The Bougainvillia ([Fig. 92]), is one of our most common Jelly-fishes, frequenting our wharves as well as our sea-shore during the spring. The tentacles are arranged in four bunches or clusters at the junction of the radiating tubes with the circular tube, from which they may be seen extending in every direction whenever these animals remain quietly suspended in the water,—a favorite attitude with them, and one which they retain sometimes for days, seeming to make no effort beyond that of gently playing their tentacles to and fro ([Fig. 92]). These tentacles are capable of immense extension, sometimes to ten or fifteen times the diameter of the bell. The proboscis is not simple as in the Sarsia, but looks like a yellow urn suspended at its four corners from the chymiferous tubes. The oral opening is entirely concealed by clusters of shorter tentacles surrounding the mouth in a close wreath, on which the eggs are supported. A highly magnified branch of the Hydroid stock from which this Medusa arises is represented in [Fig. 93]. There we see the little Jelly-fishes in different degrees of development on the stem, while in Figs. 94-97 they are given separately and still more enlarged. In [Fig. 94] the outline of the Jelly-fish is still oval, the proboscis is but just formed, and the tentacles appear only as round swellings or knobs. In [Fig. 95] a depression has taken place at the upper end, presently to be an opening, the proboscis is enlarged, and the tentacles lengthened, but still turned inward. In [Fig. 96] the appendages of the proboscis are quite conspicuous, the tentacles are turned outward, and the Jelly-fish is almost ready to break from its attachment, having assumed its ultimate outline. [Fig. 97] represents it just after it has separated from the stem, when it has only two tentacles at each cluster and simple knobs around the mouth, instead of the complicated branching tentacles of the adult.