Page:Popular Science Monthly Volume 8.djvu/31

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21
HYDROIDS.

both organic matter in solution and oxygen; and that this same water, after having passed through the bodies of these lower forms of animal life, is deprived of both its organic elements and its oxygen. The theoretic difficulty which had determined the problem of life in the depths of the sea was thus removed; for, given this lowest form of animal existence, the higher are always possible.

The same awful cycle of life, death, decomposition, and life again, which is again and again repeated among the higher organisms, is found working itself out as inexorably in the oceanic depths. The elements which are appropriated from the mighty reservoir of the ocean for the maintenance of the life, are restored to it again by the death, of each organic being.

The bed of the ocean, from the tiny lakelets left by the retiring tide to the greatest depths ever reached by trawl and dredge, is found to be teeming with exquisite forms of life. Delicate plant-like forms are found clinging to rocks and shells, or spreading themselves over the broad fronds of the algae. Every peculiarity of vegetation is mimicked; graceful stems rising from tangled roots send out branches which bear raceme-like clusters of buds, and delicate bells whose beauty no words can describe.

PSM V08 D031 Roving medusa of tubularia indivisa.jpg
Fig. 5.—Roving Medusa of Tubularia indivisa. (Magnified.)

A hundred and fifty years ago nothing was known of these beautiful hydroids. The first investigation deserving the name was made by Abraham Trembley. This man was born in Geneva in the year 1700. While residing at the Hague, as tutor to the sons of Count de Bentinek, he made a series of remarkable observations upon the fresh-water hydra. The results of his observations were published first by Réaumur in 1742, and two years later by himself. In 1727 Peysonnel had paved the way for Trembley by proving the animality of the corals. Jussieu visited the coasts of Normandy to investigate the coral question, after Peysonnel's publication of his views, and there conclusively demonstrated the animality of Tubularla indivisa, one