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182 ACTINOZOA. 



age. 



notwithstanding their increased differentiation of 

 tissue, appear fully to rival the Hydrozoa. Many 

 experiments show how complete may be the healing 



refisener 



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Of the duration of life among the Actinozoa, 

 as among Coelenterata in general, we are still very | t 

 ignorant. Some Ctenophora appear to last but a 

 single season, yet this statement can by no means 

 be regarded as true of the entire group. The j ] 



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Alcyonaria and Zoantharia seem long-lived and 

 hardy animals, a specimen of the common Sea- \ I 

 anemone, kept in confinement for forty years, 

 showing no visible signs of decrepitude or old a 



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In reparative power the members of this class, , i 



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large number of Actinozoa. Occasionally the pro- t 



cess of reparation displays itself in a curiously t 



abnormal manner. Thus, a section having been 

 made below the disc of a Sea-anemone, tentacles 

 were developed from both of the fresh surfaces 

 thus exposed. 



A common British Zoantharian, Anthea cereus, \ 



adapts itself well to the conditions of such experi- \ 



ments. Artificial fission of this species, if per- t 



formed with care, does not always result in death | { 

 of the parts so divided. 



The same animal may also illustrate the mode 

 in which spontaneous fission occurs among many 

 other forms of Actinozoa. A longitudinal cleavage 

 of the polype commences, in most cases, across 

 the region of the disc, and thence proceeds down- 

 wards towards its proximal extremity. 



Less frequently is fission effected by the separa- 

 tion of small portions from the attached base of 

 the primitive organism, whose form and structure 



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