Image from page 172 of "Ocean wonders: a companion for the seaside" (1879)
Authors: Damon, William Emerson, 1838-
Publisher: New York, D. Appleton and company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress
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duction and growth are so anomalous as to have long baffledthe investigations of naturalists. Their nature is now betterknown, but we suspect there is much yet to be learned inregard to them. The hydroids are compound animals which produce in-dividuals ; and these individuals in their turn produce com- HYDROIDS, MEDUSAE, ETC. 151 pound progeny. Some of them look like shrubs, youngtrees, or bushes, and only minute investigation proves themto possess vitality, and to be in fact communities of indi-viduals arranged in a plant-like form; from these may behatched a single jelly-fish or medusa, and from the medusawill eventually be produced a group of hydroids. The hydroids belong to the division Acalephce, and areas a general thing semi-transparent, fragile, and often verygraceful objects, yet not always so harmless as they look. In
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Adult Sun-Fish, or Jelly-Fish (Aurelia, Agassiz). this division are included the large families of the campa-nularians, sertularians, tubularians, and others. The varietyof their forms is almost infinite. Some float through theseas like a branch covered with bell-shaped flowers; othersappear like groups of disks or cups; some are vase-shaped,some oval; some are iridescent spheres; some form gar-lands, or trail along like endless fringes; while possibly themost common and best known form is the umbrella shape,of which the beautiful haired medusa is the finest represent-ative, Q 152 THE OCEAN. When the hydroid is in the compound state, the plant-like community is enveloped with a thin covering of a hornynature, which also covers the hell-like cellules in which theprogeny are developed. When the latter arrive at a suffi-cient degree of maturity, this covering bursts and allows theescape of the young medusae. These productive cellules arealways developed in the angles formed by the juncti
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