Marvels of Pond-Life. 99 



few pieces of straw, or a tiny wisp of hay, we shall 

 succeed much better, and not only preserve our popula- 

 tion longer, but enjoy a succession of animated crops. 

 Extensive decomposition of vegetable matter kills off 

 all but certain families, such as Paramecia, who enjoy 

 it; on the other hand, too little decomposition proves 

 fatal to some creatures, by depriving them of their food, 

 and when they have died off, those who depended upon 

 them for a living, die too. Different vegetables in 

 decomposition suit different creatures, and hay and 

 straw in that state seem to please the largest number. 

 An animalcule tank will succeed best when it contains 

 two or three kinds of growing plants, which oxygenize 

 the air, and a moderate variety of decomposing or- 

 ganisms will supply food without making the water 

 offensive. 



From these considerations it will be apparent that 

 not only the nature of the vegetation of a pond, which 

 is often changed by accidental circumstances, but also 

 the quality of the odds and ends that the winds may 

 blow into it, or which may fall through the air, will do 

 much to determine the character and number of its 

 inhabitants, while the quantity of shade or sunshine it 

 enjoys, will also exercise an important influence. Hay 

 and other infusions have from the beginning of micro- 

 scopic investigations been employed to obtain the 

 creatures which the Germans call "Infusions thier- 

 chen" (infusion animalcules), and the English " Infu- 

 soria ;" but very little has yet been done in the way of 

 their scientific culture and management. 



To return from this digression to our little Hamp- 



