S E R T U L A R I A. 



In my EfTay on Corallines, page 32, 1 have taken no- 

 tice that the branched tubular Coralline was like the 

 Hydra, or frefli- water Polype ; but with this difference, 

 that on account of its expofed fituation in the fea, nature 

 had clothed it with a horny fkin. And in this genus or 

 Sertularia, nature has been ftill more favourable in pro- 

 viding little cup-like denticles to fecure their many ten- 

 der heads fafe, when they are drawn in upon any alarm 

 of danger ; whereas the heads of the tubular Corallines 

 have no fuch prote&ion, for which reafon they are not fo 

 often found in the turbulent parts of the ocean as in fhel- 

 tered recedes of harbours. 



It is well known, that the young of fhell-lifli are pro- 

 duced with the fhell upon them ; the young fea polypes 

 have alfo their proper horny covering on, fo that the fol- 

 lowing obfervations will appear agreeable to truth. The 

 young animal difcharged from its ovary adheres by its bafe, 

 and with its claws quickly procures nourishment fufficient 

 to increafe its bulk : by this means, then, the ftem ad- 

 vances, and many more heads with their claws come 

 forth, and ftretch themfelves out for food ; this caufes a 

 further increafe of nourifhment to be drawn in by thefe 

 additional active organs, which circulates through the 

 whole animal, and enables it, agreeable to the order of 

 nature, to fend forth from its bafe creeping adhering tubes 

 full of the fame living medullary fubftance with the reft 

 of the body. Thefe tubes not only fecure it from the 

 motion of the waves, but likewife from thefe rife other 

 younp- animals or Corallines, which growing up like the 

 former, with their proper heads or organs to procure 

 food, fend out other adhering tubes from below, with a 

 further increafe of thefe many-headed branched animals; 

 fo that in a fhort time a whole grove of vehicular Coral- 



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