INFUSORIAL ANIMALCULES. 23 



dormant in dry sand for four yeats. Nor is this all ; for such is the tenacity 

 of life in these minute beings, that the same animalcule may repeatedly pass 

 through these phases of existence before it really expires. Mantell remarks that 

 some wheel animals were alternately dried and rendered torpid, and then again 

 revived twelve times, and at each resuscitation were as active as at first. 



The eleventh revival was witnessed by Spallanzani ; and he leads us to infer, 

 that upon moistening a portion of sand containing wheel-animalcules for the 

 fifteenth time, many of them once more awoke from their stupor ; but this was 

 the last effort of vitality, for upon being dried and moistened again, no resuscita- 

 tion occurred. The wonderful legend of the Seven Sleepers is here more than 

 realized ; and in the Infusorial world the romantic fiction of Rip Van Winkle 

 becomes a sober statement of fact. Thus it is that Fancy in her wildest flights 

 seldom sweeps beyond the circle of truth. 



It is the opinion of Dr. Ehrenberg, in regard to this subject, that if the ani- 

 malcule is entirely dried up and its natural heat lost, life is extinguished, but if 

 this is not the case the creature will remain in a torpid and motionless state, 

 capable of being revived ; its body wasting away to an extent equal to the 

 amount of nourishment necessary for the support of its life, 



INFLUENCE OF TEMPERATURE. Infusorial animalcules are capable of existing 

 throughout a great range of temperature, but eventually perish under extreme de- 

 grees of heat and cold. If water filled with Poly gastric Infusoria is gradually raised 

 to a temperature of 125 Fah., the creatures still live ; and Dr. Ehrenberg re- 

 marks that in one instance several animalcules of a certain kind continued alive 

 at the temperature of 200 Fah. If the increase of heat is sudden, they perish 

 at 140 Fah., although the temperature is maintained for only half a minute. 

 Some kinds, however, are extremely sensitive, and are unable to endure an or- 

 dinary degree of warmth. This is the case with the Bell-flower animalcule, 

 which dies under examination in a hot room. Most of the Polygastrica retain their 

 vitality at temperatures considerably below the freezing point; but when the mer- 

 cury descends as far as 7 or 8 Fah., many species can no longer exist. One kind 

 of the Bell-flower animalcule still lives after being exposed to a temperature of 

 8 Fah., and the ice then gradually thawed in which it was frozen ; but not more 

 than one individual in a hundred can survive this ordeal. The Rofcatorial ani- 

 malcules are more susceptible, and perish when the cold is less severe. 



During the Antarctic expedition under Capt. James Ross, animalcules were 

 found existing in great abundance in those inclement regions. In the sediment 

 obtained from melted ice, floating in round masses, in the latitude of 70, more 

 than fifty species of loricated Infusoria were discovered alive, notwithstanding the 

 extreme cold to which they had been exposed. According to Dr. Ehrenberg, 

 when a layer of clear ice containing animalcules is examined under a low tem- 

 perature by the microscope, each animalcule or group will be seen surrounded 

 by a very small portion of water, which he supposes is prevented from freezing 

 by the natural heat of their bodies ; and he likewise believes that death inevita- 



