HYDRA. 73 



CHAPTER III. 



THE HYDRA OR POLYPUS. 



The preceding facts, sufficiently interesting in themselves, require 

 some farther illustration, for explaining the general nature of the hydra 

 or polypus, so often referred to as forming a most essential part of the 

 subjects described. This will enable the reader to comprehend still more 

 satisfactorily the peculiar quality of those to follow, especially if never 

 having himself beheld them in their native element. 



From the material difference of organization in those living beings, 

 which, along with inorganic matter, compose the substance of such ani- 

 mal products passing by the general appellative of Zoophytes, the name 

 hydra is employed rather as a conventional term than as a definition, to 

 signify that active portion endowed with evident sensation and spontaneous 

 motions. Custom has sanctioned its application, like the use of other 

 phraseology : it is attended with certain facilities ; and it may tend to re- 

 press that inordinate multiplication of trivial nomenclature whose subdivi- 

 sions threaten confusion to both the learned and the illiterate in the maze 

 of interminable ramifications. 



Had this work been more than a mere collection of memoirs from 

 practical observations — a siinple detail of facts — the useful arrangements of 

 Dr George Johnston might have been beneficially followed as a guide ; for 

 that learned author, commencing with the hydra, lays down the elements 

 of an easy partition of zoophytes, founded on the nature of the animated 

 portion. He distinguishes them as Hydraoidal, Ascidioidal, Helianthoidal, 

 and Carnose. 



In as far as I am aware the hydra proper — that is, the polypus of 



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