Sentence Examples


  • Each Graptolite represents the common horny or chitinous investment or supporting structure of a colony of zooids, each tooth-like projection marking the position of the sheath or theca of an individual zooid.
  • In Dictyonema the branches show thecae of two kinds: (I) the ordinary tubular thecae answering to those of the Graptoloidea and occupied by the nourishing zooids; and (2) the so-called bithecae, birdnest-like cups (regarded by their discoverers as gonothecae) opening alternately right and left of the ordinary thecae.
  • 14), forms arborescent colonies consisting of numerous zooids arranged in a single series along one surface of a branched horny axis.
  • After division the corallites continue to grow upwards, and their zooids may remain united by a bridge of soft tissue or coenosarc. But in some cases, as they grow farther apart, this continuity is broken, each corallite has its own edge-zone, and internal continuity is also broken by the formation of dissepiments within each calicle, all organic connexion between the two zooids being eventually lost.
  • The lastnamed method has proved little more than that there is a remarkable similarity between the zooids of all recent corals, the differences which have been brought to light being for the most part secondary and valueless for classificatory purposes.
 

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