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But there is a great difference in the oral apparatus; the elaborate ruffled curtains, that hang from the corners of the mouth, occur only in the Species arising from the transverse division of the Polyp-like young. For this reason they are divided into two Orders, the Hydroids and the Discophorae. The third Order, the Ctenophorae, are among the most beautiful of the Acalephs.
It would be hopeless, even were it desirable, to attempt within the limits of such an article as this to give the faintest idea of the number and variety of these Hydroids; and I will therefore say nothing of the endless host of Tubularians, Campanularians, Sertularians, etc.
In the Hydroids, the organization does not rise above the simple digestive cavity inclosed by the double body-wall; and we might not suspect their relation to the Acalephs, did we not see the Jelly-Fish born from the Hydroid stock.
The Yekta of the Crimson Sea, are as extraordinary developments of hydroid forms as the giant Medusae, of which, of course, they are not too remote cousins. The closest resemblances to them in outer water forms are among the Gymnoblastic Hydroids, notably Clavetella prolifera, a most interesting ambulatory form of six tentacles.
But if such a little tuft of Hydroids has been gathered in spring, a close observer may have an opportunity of watching the growth of another kind of individual from it, which would seem to show its alliance with the Acalephs rather than the Polyps.
These are young medusæ or jelly-fish, which grow like bunches of currants, and later will break off and swim around at pleasure in the water. Occasionally one is fortunate enough to discover these small jellies in a pool where they can be photographed as they pulsate back and forth. When these attain their full size they lay eggs which sink to the bottom and grow up into the plant-like hydroids.
It is true that the Hydroids live along the shore, and may be reared in tanks without difficulty; but they are small, and would be often taken for sea-weeds by those ignorant of their true structure.
Much of the seaweed from deeper bottoms seems to be covered with a dense fur, which under a hand lens resolves into beautiful hydroids, near relatives of the anemones and corals. Scientists have happily given these most euphonious names Campanularia, Obelia, and Plumularia. Among the branches of certain of these, numbers of round discs or spheres are visible.
The demonstration of the unity of plan pervading the diversities of the Polyps, Hydroids, Acalephal and Echinodermal modifications of your truly natural group of Radiates, is to my mind perfect, and I trust that the harsh and ugly and essentially error-breeding name of Coelenterata may have received its final sentence of exile from lasting and rational zoological terminology.
One day she asked for a book on 'Gymnoblastic Hydroids'; the amazing title in the catalogue had filled her with curiosity; she must know the meaning of everything. She was not idle, Emily. But things in the home were going from bad to worse. When Emily was sixteen, her father scarcely knew where to look for each day's dinner. Something must be done. Activity took a twofold direction.
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