372 Fossil and Recent Infusoria. 



hitherto discovered was above 28 feet in thickness, near Lune- 

 bourg ; that however similar layers have already been found in 

 Africa, Asia, and the South Sea Islands. At the same time I 

 noticed that I had succeeded in artificially preparing from still 

 existing Infusoria very considerable quantities of earth. I ex- 

 hibited a large glass full of such artificial siliceous earth, in which 

 the microscope, however, still evidently and distinctly discovers 

 all the forms of the Infusoria constituting it, pounds and tons of 

 which earth may easily be prepared. I mentioned in few words 

 the still existing controversy between botanists and zoologists, 

 both of whom would class in their catalogues these microscopic 

 living forms ; and I briefly noticed the reasons given in detail in 

 my work for each opinion, deciding myself in favor of their being 

 animals. 



I also said a few words on the luminosity of the sea, which 

 subject in part stands in immediate connection with these micro- 

 scopic animals, it being regarded an act of animal life ; and I in- 

 vited attention to the fact that the luminosity in Infusoria and 

 Annulata is an evident voluntary production of sparks, so that in 

 the latter there originates a light apparently continuous and tran- 

 quil to the naked eye, from numerous microscopic sparks follow- 

 ing each other in quick succession. The analogy with electrical 

 phenomena is very close, and it is especially worthy of attention, 

 that evidently the smallest animals give the largest sparks, in pro- 

 portion to the size of their body, and consequently very probably 

 produce the greatest electrical tension. 



I then mentioned the curious formation of double gems in 

 Closteinum and in the ConfervcB conjugatcB, which is figured in 

 the plates of the family of the Closterinm, and I concluded with 

 a remark on the astonishing great fertility or capacity of increase 

 of microscopic animals, according to which an imperceptible cor- 

 puscle can become in four days 170 billions, or as many single 

 individual animalcules as contained in 2 cubic feet of the stone 

 from the polishing slate of Bilin. This increase takes place by 

 voluntary division ; and this is the character which separates ani- 

 mals from plants. It is true, that the gemmation in plants, 

 especially in very simple cells, is at times very similar to the di- 

 vision in animals, but this relates to the form, not the formation. 

 A vegetable cell apparently capable of self division always became 



