File:The fauna of the deep sea (1894) (14761137834).jpg

Identifier: faunaofdeepsea01hick (find matches)
Title: The fauna of the deep sea
Year: 1894 (1890s)
Authors: Hickson, Sydney John, 1859-1940
Subjects: Marine animals
Publisher: New York D. Appleton and Company
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

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found between tide-marks or in depths ofless than fifty fathoms. The Pennatulids, on the other hand, are rarelyfound in very shallow water, and nearly half theknown genera live in deep water. At least twofamilies may be said to be characteristically abysmal.These are the Umbellulid^ and the Protoptilidge. The Pennatulid^e are regarded by naturalists asthe most complicated or highly organised group ofthe Alcyonaria. Three different forms of polype buildup the colony or sea-pen as it is called. There isa single very much modified and enormously largepolype, without tentacles, forming the axis, a largenumber of ordinary Alcyonarian polypes (autozooids)arranged in the form of leaves, or simply scatteredirregularly on the surface of the central polype, anda number of very small undeveloped polypes(Siphonozoids) without tentacles, whose functionseems to be to pump water into the canals of thecolony, and thus to keep up the circulation of water. The deep-sea genus Umhellula possesses a very
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Fig. 10.—Umbellula Giintberi. Nat. size, ^fter Agassiz. 98 THE FAUNA OF THE DEEP SEA long and delicate axial polype, and the Autozooids andSiplionozooids form a little cluster only at its extremesummit. The small number of these polypes andthe very limited area over which they extend are thetwo most characteristic features of the genus. Itwould take me too far into the anatomy of the groupif I were to add any further details ; but I cannot passon without noting that the whole structure ofUmbellula shows that it is far more primitive andsimple than the shallow-water genera. And, generallyspeaking, this holds good for all the deep-sea Pen-natulids. In fact, we have here one of the rare ex-amples of a series of genera, that can be regarded asa slightly modified ancestry of the shallow-watergenera, that has been brought to light by the explora-tion of the abysmal depths of the ocean. We have seen, then, that of the Coelentera, theonly order that has a large proportion of its generalivin

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