82 NATURAL HISTORY RECREATIONS. 



led rotatory organ, which is surrounded by hairs and situated near the 

 mouth, and this is kept in constant motion. Some have stiff bristles, 

 hooks, claws, spurs, beards, and snouts. Other organs of sense have 

 not been discovered, for the four or five black or red spots over the 

 mouth, which have been regarded as eyes, have other offices to perform. 



The minutest infusories are sustained only by absorption through 

 the surface of the body. But the more perfect species take their nour- 

 ishment through the mouth, and this consists of still smaller infusory 

 animals. The rotary (or wheel) animals by tlie motion of their singular 

 organ produce an eddy in the water, and thus their food is forced into 

 their mouths. Others have their raoulhs surrounded by a cutaneous 

 sheath which can be folded in all directions. In some, this sheath is 

 reniform, and the edge is covered with hairs. When the animal extends 

 the sheath, and moves the hairs, all smaller species in the vicinity are 

 entrapped, as it were, and sucked into the mouth. 



The origin of infusories has been a fruitful theme of speculation. — 

 Many believe that they proceed from eggs as other animals, or from di- 

 visions or sprouts from their parents, and some maintain that they are 

 the product of spontaneous or equivocal generations. This latter sup- 

 position cuts the knot of the difficulty, but it is not satisfactory. Many 

 curious facts have been stated to prove this theory, but it is not now 

 generally entertained by naturalists. 



It is remarkable that the same water or infusion will by degrees con- 

 tinue to develop different species of these animals, and that they suc- 

 cessively become more perfect in their organization. At first, the water 

 is literally alive with tlie most infinitesimal monads, — after a few days 

 other species will take their place, — afterwards others of a different for- 

 mation and more distinct members. 



Although infusories are originally generated like other animals, yet 

 after their full development they multiply by voluntary separation, and 

 by so called eggs, or germinal grains. You will frequently observe on 

 both sides of the body of one of them, a deep incision, which gradu- 

 ally becomes deeper, and finally the animal is separated in two. Each 

 grows as large as the first individual, and then they divide in the same 

 manner. The so-called eggs of infusories are not really such, but are 

 only germs, and they are giadually developed to a perfect animal, with- 

 out breaking the shell as is the case with animals hatched out of real 

 eggs. Their powers of reproduction are prodigious, and according to 

 Ehrenberg, in from eight to fourteen days they multiply to millions, es- 

 pecially when the circumstances are favorable. Even during this win- 

 ter, I have observed the same phenomenon, and a summer or two ago, 



