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no progress in development in them, the function is 

 possessed by them in a much higher degree. The three- 

 fold classification of these animals into — 1st, Hydrozoa ; 

 2d, Anthozoa; and 3d, Bryozoa, was adopted, and the 

 Hydra Viridis taken as an example of the first class. This 

 creature, although the type of the lowest organized group, 

 is the most locomotive of the Polyp-tribe. It is not possessed 

 of any organs having locomotion for their sole, or even prin- 

 cipal object. Its movements from place to place are effected, 

 sometimes by a kind of gliding, performed by bending the 

 body so as to bring the tentacular extremity to the plane of 

 motion, to which the tentacula attach themselves at some 

 distance from the basal termination ; this, then quits its 

 hold and is made to approach the tentacula, when the 

 sucker again attaches to the body on which the movement is 

 being made; the tentacula again advance, and are a second 

 time followed by the sucker-end, and so on until the desired 

 migration is completed. At other times the creature quits 

 its hold entirely and commits itself to the waters which it 

 inhabits, to the surface of which it soon rises, where it is 

 supported by the now-expanded sucker-disc, and is thus 

 transported by the motion of the waters, or wafted by the 

 wind, to a new locality. The muscular contractility necessary 

 to these movements seems to be produced by the nucleated 

 cells intermediate to the two external layers of elongated 

 cells, forming the parieties of the tubular body. 



The Actinia was selected as an example of the Anthozoa. 

 Its powers of locomotion were shewn to be considerable. 

 The means of effecting it was, by gliding on the basal-disc 

 by an arrangement of strong muscular fibres ; or by filling 

 the body with water, when they detach themselves entirely, 

 like the Hydra, and float away. Here again the cilia are 

 employed as organs of locomotion by the Animals in the 

 gemmule state. 



In the Actinia?, we have the first decided appearance of 



