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Microscopical Essays. 



The polype does not always wait for it's prey, it feels for it, 

 and in a manner follows it. It may be afked, how can it do this 

 when it has no eyes ? or, do the glandular grains anfwer this 

 purpofe ? Who can anfwer the queftion ? what are our own eyes 

 but glandular grains of a larger fize ? If this mould be the cafe, 

 our hydra would again exceed and realize the fables of the an- 

 cients, being an argus entirely compofed of eyes. Be this as it 

 may, they are certainly in pofleffion of fome fentiment by which 

 they can perceive the approach of their prey, and which renders 

 them attentive to all that may confirm or deftroy this perception. 



When the arms of a polype are extended, put a millepedes, or 

 any kind of worm, into a glafs, (fee Fig. 1, PI. XXIV. A) and with 

 the point of a pencil pufh it towards one of the arms ; as foon as. 

 it touches this it is feized ; the worm, or millepedes, endeavours 

 by quick and ftrong efforts to difengage itfelf, often fwimming and 

 dragging the arm from one fide of the glafs to the other. This 

 violent motion of the prey obliges the polype to contract ftrongly 

 the arm, in doing which it often twifts it in the form of a cork- 

 fcrew, as at o i, by which means it fliortens it more rapidly : the 

 ftruggles of the devoted animal foon bring it in contact with ano- 

 ther arm, thefe contracting further, the little creature is prefently 

 engaged with all the arms, which contract fo much as to convey 

 it to the mouth, a gain ft which it is held and fubdued. 



* When a polype has nothing to eat, it's mouth is generally 

 open, but fo fmall that it can fcarce be perceived without the 

 afhftance of a magnifying glafs'; but as foon as the arms have 

 conveyed the prey to the mouth, it opens itfelf wider, and this in 

 proportion to the fize of the animal that is to be devoured ; the 



