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 SeaTIslands. 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 ‘zodlogists, 
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 
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 intima and 
Annulata is an evident voluntary production of sparks, so that in 
the latter there originates a light apparently continuous and tran- 
guil 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, nt consequently very probably 
produce the greatest electrical tension. 
I then mentioned the curious formation a double gems in 
Closterium and ih the Conferve conjugate, which is figured in 
the plates of the family of the Closterine, 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 
