A colony of <i><a href="//commons.wikimedia.org/wiki/Category:Cladonema_radiatum" title="Category:Cladonema radiatum">Cladonema radiatum</a></i>, magnified. The drawing has been made from the free variety of this hydroid.
<bdi><a href="https://en.wikipedia.org/wiki/en:George_Allman_(natural_historian)" class="extiw" title="w:en:George Allman (natural historian)"><span title="Irish natural historian (1812-1898)">George James Allman</span></a>
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Allman G. J. The Monograph of the Gymnoblastic or Tubularian Hydroids. –  Conclusion of Part I and Part II. – London: Robert Hardwicke, 1872. – <a rel="nofollow" class="external text" href="https://www.biodiversitylibrary.org/item/37418#page/75/mode/1up">Plate XVII</a>