STILL FOUND IN A LIVING STATE. 341 
1000 different known forms, the chief mass of chalk rocks and 
of many sea-sands. Dujardin, on the other hand, had subse- 
quently denied to these animals all organic structure, and as- 
serted them to be simple living and extensile slime, encased 
by a hardened external shell. 
In my observations on the formation of the chalk from micro- 
scopic animals presented to the Academy in 1838 (where also 
historical notices relative to this subject are collected), the great 
influence of these minute bodies on such rock formations was 
explained. From the observation of a living species in the Red 
Sea, and by moistening the small dried bodies of several such 
forms taken from the sea-sand, and dissolving the delicate 
calcareous shell from the body in weak acids, by means also 
especially of the knowledge gradually acquired from rendering 
the shells transparent by the process there stated, they were 
classed with the Moss-coral animals (Bryozoa?). Finally, 
the interest in these minute bodies was heightened from the 
circumstance of two of those forms (Planulina (Rotalia?) tur- 
gida, and Textilaria aciculata), which help to constitute the 
great mass of the chalk by their incalculable number, having 
(in perfect opposition to existing general geological phenomena) 
been detected still living in Berlin in the sea-water collected at 
Cuxhaven in Sept. 1839. But further details of the organiza- 
tion could not be established. 
_ From the importance which Nature imparts even to these 
minute organisms, which she has placed indeed, in individual 
energy, far below lions and elephants, but in their more ge- 
-neral social influence far above them; and from the fluctuation 
in the opinions of naturalists on the true nature of these minute 
bodies, caused by the difficulty of examination, it may not be 
amiss to add, at the earliest opportunity, some recent observa- 
tions to what I have before communicated. I have indeed the 
pleasure to exhibit alive to the Academy (Jan. 16th, 1840) ten 
such animalcules, in form resembling an Ammonite or Nautilus, 
of a size easily visible, together with drawings, and to solve all 
doubt as to the main points regarding the nature of these bodies. 
iy The forms observed in October of last year (living chalk ani- 
malcules) were very minute, and exhibited, it is true, organic 
contents and locomotion, but no external organs. I was as lit- 
tle successful in clearly discriminating the internal organization. 
Those which I exhibit today are (not indeed forms observed 
as haying existed at the period of the chalk formation, but) so 
