INFUSORIES. 161 



ducing a vortex like the rotatories, 1 thus find an 

 abundant supply to carry them to their interme- 

 diate state. But not only do these creatures 

 furnish the more minute animals that inhabit 

 the waters, with a considerable portion of their 

 food, but, it should seem, even some of those 

 that are of a higher grade, and larger stature. 

 Whoever has been in the habit of keeping gold 

 and silver fish, 2 in glass or other vessels, is aware 

 that they require no other food than a fresh 

 supply of water every second or third day. 

 Their nutriment therefore must be derived 

 from what they find in the water. In this may 

 often be seen minute Branchiopods swimming 

 here and there, sometimes with a bundle of eggs 

 appended to each side : but these are not 

 sufficiently numerous to form the whole of their 

 food, the water must therefore contain other 

 nutritive substances which may contribute to 

 their subsistence, and as it is known that various 

 infusory animalcules inhabit it, we may conclude 

 that they are inserted in their bill of fare. It 

 has been observed by an eminent writer, 

 speaking of the gold fish, "The water, when 

 care is taken to renew it frequently, appears suf- 

 ficient for the nutriment of these fishes during 

 many months ; but it should be considered that 

 though this water appears to us very pure, 



1 Culex, Stratyomis, &c. 2 Cyprinus auratus. 



VOL. I. M 



