The mode of growth in this axis presents great variations. Sometimes it remains simple and rises like a slender rod, sometimes it has numerous branches. It is _arborescent_ when the branches and their accompaniments take different directions so as to constitute tufts. It is _panicled_ when they arrange themselves on both sides of the stem or principal branches, after the manner of the barbs of a feather. It is _flabelliform_ when the branches rise irregularly under the same plane; _reticulated_, when branches are so disposed as to be attached to each other by network in place of remaining free. The _Gorgoniadæ_ are found in every sea, and always at considerable depths. They are larger and more numerous between the Tropics than in cold or even temperate climates. Some of these corals scarcely attain the twelfth of an inch in height, while others rise to the height of several feet. [Illustration: Fig. 44. Gorgonia verticellata (Pallas).] Formed in the bosom of the ocean, it is only necessary to behold these singular creations in order to admire the brilliant colours which decorate their semi-membranaceous branches. The brilliancy of their robes are singularly diminished, have almost entirely disappeared, indeed, when they make their appearance in the cases of our natural history collections. The _Fan Gorgon_, from the Antilles (Fig. 42), is a species which often attains the height of eighteen or twenty inches, and nearly as much in breadth. The network of its interstices with its unequal and serried meshes, resembling fine lace, have led to its designation of _Sea Fan_. Its colour is yellow or reddish. In Fig. 43 we have the _Sea Fan_ magnified to twice its natural size, showing the curious details of its organization. [Illustration: Fig. 45. Gorgonia verticellata (Pallas), magnified four times.] The Whorled Gorgon (_G. verticellata_), which is found in the Mediterranean, is yellowish in colour, and also of elegant form. It is sometimes called the Sea Pen. This species is represented in Fig. 44, while Fig. 45 represents a small branch magnified four times, in order to give an exact idea of its form. The Gorgons are not known to be useful either in the arts or in medicine. They are ornamental in cabinets, and interesting both as objects of study and of zoological curiosity. ISIDIANS. The _Isidæ_ constitute an intermediate group between the _Gorgons_ and _Corallines_. Their polypidom is arborescent, but its axis is formed of articulations alternately calcareous and horny. The principal genus is that of the _Isis_, which is met with in the Indian Ocean, on the American coast, and in Oceania. The inhabitants of the Molucca Islands use these animals medicinally as a remedy in certain diseases; but as they use them for the most opposite maladies, it may be doubted if they are really efficacious in any medicinal point of view.