Page:Popular Science Monthly Volume 8.djvu/36

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the somatic flow is observed the like cause may account for the like effect.

The exquisite colors of the hydroids, which rival the tints of our loveliest flowers, are due to the colored granules secreted by the animal and discharged into the somatic fluid. A charm is added to these flowers of the sea by the flashing opalescent gleams of color which shine out from their crystalline walls. Even the exquisite representations of Allman, in his monograph on "The Tubularian Hydroids," fail to give an idea of the beauty of form and color to be found in the real object. The Hydra viridis is so called from its brilliant green color. This green is said by Allman to be of the nature of chlorophyll, and to possess the power, like the chlorophyll of plants, of decomposing carbonic acid, assimilating the carbon, and yielding up the oxygen. If this be true (and there is no reason to doubt it, Allman being one of the highest authorities), it only furnishes, in this form of animal life, one more curious resemblance to vegetation, and denies one more tradition of its animality.

PSM V08 D036 Sertularina cupressina.jpg
Fig. 8.—Sertularina cupressina. (Magnified.)

The most singular facts in connection with hydroid life lie in the variety of its modes of reproduction. It would almost seem as though every form of reproduction known in Nature had been mutely prophesied in the primeval world when the fossil hydroid and trilobite lived side by side in the Silurian seas.

They are generated, like plants, by buds and by artificial sections; like plants, they are able, from a small fragment, to produce the whole organism. They, however, go farther than most plants in this power of reproducing lost parts; for a small fragment taken from any por-