KOTIFERA. 39 



through the winter, and revive when their little ice-houses have been 

 melted away in spring. 



Infusoria are destroyed generally by expanding and bursting, after 

 a few minutes' subjection to the heat of boiling water. 



In water subjected to a galvanic current strong enough to cause de- 

 composition, the contained Infusoria are killed. When subjected to a 

 weaker current, those only which came into its course were affected : 

 some Rotifera were observed to be stunned only, and afterwards re- 

 covered ; others were killed. 



Tenacity of life is a very striking physiological character of the 

 Infusoria, 



The famous phenomena of the revival of Rotifera^ after having 

 been completely dried and apparently killed, certainly when reduced 

 to the state of the most complete torpidity, \vere first observed by 

 Leeuwenhoek in the year 1701. The father of microscopical anatomy 

 had been engaged in examining some specimens of Rotifer vulgaris 

 with Euglena sangiiinea, and had left the w^ater in which they were 

 contained, to evaporate. Two days afterwards, having added some 

 rain-water, which he had previously boiled, within half an hour he 

 saw a hundred of the Rotifera revived and moving about. A similar 

 experiment was followed with the same result after a period of five 

 months, during which period the Rotifera had remained in a state of 

 complete desiccation and torpidity. These observations were re- 

 peated by Baker and J. Hill. You will find all the experiments 

 that were recorded before the time of Haller accurately quoted in his 

 great '' Physiologia Corporis Humani," vol. viii. p. 111. Fontana kept 

 Rotifera two years and a half in dry sand, exposed to all the power 

 of an Italian summer's sun : yet in two hours after the application of 

 rain-water they recovered life and motion. 



Goze, Corti, and Miiller record similar experiments ; but those 

 performed by the celebrated Abbe Spallanzani are perhaps most 

 generally known. 



He succeeded in reviving his Rotifers after four years' torpidity : 

 he alternately dried and moistened the same animalcules twelve times 

 with similar results, except that the number of the revivers was suc- 

 cessively smaller ; after the sixteenth moistening he failed to restore 

 any of them to life.* 



One of the essential conditions of the revival of the Rotifers 

 appeared to Spallanzani to be their burial in sand : the access of air 

 seems prejudicial to their retention of vitality. Miiller, the famous 



* Opusc. die Fis, Anim. vol. ii. p. 181. 

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