63 
stanced, but that, from the gradual longer chemical decomposition 
and change of many of its organic relations, it is more difficult to 
examine and determine. 
“* Paludina vivipara and Cyclas cornea of the Weald clay, and the 
recent Trochus below the chalk, according to Defrance, as well as the 
confirmation of the occurrence of Terebratula caput serpentis in the 
Upper Jura by Von Buch, together with my observations of micro- 
scopic yet nevertheless peculiar Polythalamia in the flints of the 
Jura, are additional positive indications of the inconceivable extent of 
similar organic relations, the further investigation of which is one of 
the important questions to be determined in the present age. 
“Since now Polythalamia, and other forms identical with chalk 
animals, exist which are not endowed with spontaneous division, 
this faculty of the Infusoria, and their general nature, are not the 
sole causes to which the indefinite duration of the species is 
owing. 
“In consequence of the mass-building Infusoria and Polythalamia, 
the secondary formations can now no longer be distinguished from the 
tertiary ; and in accordance with what has been above stated, masses 
of rock might be formed even at the present time in the ocean, and be 
raised by volcanic power above the surface, the great mass of which 
would, as to its constituents, perfectly resemble the chalk. Thus then 
the chalk remains still to be distinguished by its organic contents as a 
geological formation, but no longer as a species of rock. 
“<The power so conspicuous in the organic beings under considera- 
tion is, according to experience, so immensely great, even in its influ- 
ence on the inorganic, that with the concurrence of favourable circum- 
stances they alone might give rise to the greatest changes in the 
distribution of the solid of the earth in the shortest space of time, 
especially in the water ; and the ascertainable extent of such influences 
