22 



GENKRAt HISTORY OF 



At another place he wiites, " the germination or extension of the 

 zoospore into a tissue similar to that of the parent plant, appears to 

 me a good character to distinguish those bodies from Infusoria. Still 

 one cannot discover in this phenomenon the basis of a division 

 between the lower forms of the two kingdoms ; for vegetables occu- 

 pj-ing the lowest grade in the scries of Algae — ex. the ISTostoclimeae, 

 Palmelleae, &c., seem to have no other mode of reproduction than 

 spontaneous division analagous to that of the most simple animals." 



Section V. Effects of Tcmperatiire on Infusoria. — As \itality in 

 these creatures is not destroyed by the ordinary cold of winter, most 

 of the common Polygastrica may be found at that season in ponds 

 under the ice. The Vorticella microstoma will live after being ex- 

 posed to 8° of Fah., and the ice gradually thawed ; although the 

 munber in this case may not exceed one in a hundred. Below this 

 temperatm-e they A\dll not survive. The same may be said of the 

 Monas termo and M. spirillum, the Paramecium aurelia, Cyclidixim 

 glaucoma, Glaucoma scintillans, and Kol/poda cucullus. "When Inftisoria 

 are destroyed by the cold, no rupture or injuiy will be apparent on 

 their bodies, excepting with the Chilodon cucullus, and some few 

 others, which, under these circumstances, will often become dissi- 

 pated. The Stcntor polymorphus and Mullcri will not live many 

 hours in a temperature of 9*^ Fah. ; and arborescent Vorticella, when 

 subjected to that degree of cold, fall from the stalks and die. 



The Rotatorial animalcules cannot endure such low temperatures 

 as those above named. 



When a small quantity of water, having animalcules in it, becomes 

 frozen, and is placed under a microscope, in a cold situation, 

 Ehrenberg states that if the ice be clear, each animalcule or group 

 will evidently be surroimded by an exceedingly small portion of 

 water, which that naturalist supposes to be occasioned by the superior 

 temperature or animal heat of the creatures preventing congelation ; 

 and he is of opinion, that in all cases where this portion of the water 

 freezes, the animalcule necessarily dies. 



If the water containing polygastric Infusoria be gradually raised 

 to a temperature of even 125* of Fah., these creatures -wt-U Mve ; 

 and Dr. E. obsei-ves, that some of the Chlamidomonas pulvisculus 



