216 UTILIZATION OP MINUTE LIFE. 



formations occasioned by these animalcules, we are 

 indebted to the labours of K. and G. Forster, Cha- 

 misso (author of the " Marvellous History of Peter 

 Schlemyll"), Peron, Quoy and Guemard, Captain 

 Flinders, Lutke, Beechy, Darwin, D'Urville, and 

 Lotin. 



Alex, von Humboldt has sketched, in a charming 

 manner, their influence upon the constitution of the 

 earth's crust, in his ' { Yiews of Nature," vol. ii. 



Hydra fusca, the olive- coloured polype of our 

 ponds and ditches, may be taken as the type of this 

 class of animals. This little being was first de- 

 scribed by Trembley in 1744, but it had been pre- 

 viously discovered by Leuwenhoek in 1703. No 

 attention was paid to it, however, till the publica- 

 tion of Trembley's paper, which produced great 

 sensation, everyone's attention was drawn to the 

 subject, and it became the principal topic of the 

 day. It was given away in presents as an object of 

 great rarity ; specimens of it were sent from abroad 

 by post, and even ambassadors made it a matter of 

 engrossing interest in their relations to the foreign 

 courts. 



If a little duck-weed (Lemna) bo put into a 

 bottle of water with a wide orifice, and the bottle 

 be placed upon a table, and allowed to remain per- 

 fectly still for some hours, the Hydra contained in 

 the stagnant water will all come to that side of the 



