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Memoirs, published at the Hague, in 1743, entitled 'Me- 

 inoires pour servir a Fhistoire d^un genre de Polypes d^eau 

 douce, a bras en forme de cornes/ and also 'Baker^s 

 Natural History of the Polype,^ published likewise in 

 London, in 1743. What renders M. Trembley's work much 

 more valuable is, that it is illustrated with many plates, and 

 these from the pencil and the burin of the highly celebrated 

 engraver Lyonet. M. Trembley, of Geneva, tells us in his 

 Memoir, that in the summer of 1740, when he made these 

 discoveries, he was residing at Sargoliet, the country-house 

 of the Comte de Bentinck, at a little distance from the 

 Hague. Having taken up some water-plants from a ditch, 

 and placed them in a glass vessel, his curiosity was excited 

 by the numerous animalcules with which the water became 

 filled. While engaged in examining them, his eyes casually 

 lighted on a polype attached to a branch of the water-plant; 

 but he paid little attention to it, as, being exj)anded and 

 motionless, he thought it a little parasitical plant. Please 

 to look at the figure of the ex'paiided" Jfydra, and you will 

 see the form in which it at first presented itself to him. 

 Looking at it afterwards, he observed some motion in what 

 we now call the tentacula or feelers, but he ascribed this to 

 the motion of the water, occasioned, he conjectured, by the 



