20 DROPS OF WATER. 



as in summer, though not in such profusion : 

 they are found even under thick ice, and I have 

 frequently broken, in severe frost, the frozen sur- 

 face of a pond, and, inserting a bottle, have ob- 

 tained some most interesting kinds. Many of 

 the Polygastrica will bear a great degree of cold, 

 even more so than those of the class Hotatoria, 

 whose organization is of a higher order. 



It has, I believe, been generally observed, that 

 the more simple the organization of animals, the 

 more retentive is the creature of life, and this is 

 the case with these minute beings. The Rotifer 

 vulgaris will even bear revivification several times. 

 Dr. Carpenter relates that he tried the experi- 

 ment six times with twelve specimens, and each 

 time some were perfectly restored to animation. 



