A Monograph of the Existing Crinoids Volume 1, PT. 1

A Monograph of the Existing Crinoids Volume 1, PT. 1

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 edition. Excerpt: ...Paradoxus From The Bay Of Bengal, Showing The Relationships Retween The Rasals, Radials, And Arms (drawing Ry The Author). 133, Lateral View Of The Calyx And Froximal Columnals Of One Of Pourtales' Original Specimens Of Democrdtus Rawsonh From Barrados, Showing The Relationships Retween The Rasals, Radials, And First Frimirrachs (camera Lucida Drawing Ry The Author). 134, The Rasal Circlet And Froximal Columnals Of A Specimen Of Monachocrinus Caridreus From The West Indies (camera Lucida Drawing Ry The Author). more complicated than the rough and general sketch just presented might lead one to suppose; but it has certain ontogenetical and phylogenetical facts in its favor, and does not involve the formation of two separate plates by simple post-larval division of a primitive single plate--a process the existence of which is as yet unproven among the echinoderms. A crinoid attached by the adherence of the central plate to some solid object upon the sea floor would be subjected to a certain amount of strain from wave motion, or from the unequal movements of its own arms, as well as from the passage of other organisms. This strain would be felt along the suture connecting this central plate with the basals (or the infrabasals), and along the interbasal sutures. There are two ways of meeting this condition: (1) the basals (or the infrabasals or both) may become more upright and more nearly parallel with each other and fuse solidly with the central plate (now become a thick stalk); this has occurred in Holopus; (2) a second central plate, exactly similar to the original one, may be formed within--that is, ventral to--it, leaving a ligamentous articulation between them by which the strain is taken up, and this process may be continued indefinitely...show more

Product details

  • Paperback | 168 pages
  • 189 x 246 x 9mm | 313g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236510879
  • 9781236510877