28 THE HISTORY OF CREATION. 
organisms, as for example the Medusz, the naked molluscs 
without shells, a large portion of the articulated animals, 
almost all worms, and even the lowest vertebrate animals, 
possess no firm and hard parts capable of being petrified. In 
like manner the most important parts of plants, such as the 
flowers, are for the most part so soft and tender that they 
cannot be preserved in a recognizable form. We therefore 
cannot expect to find any petrified remains of these import- 
ant organisms. Moreover, all organisms at an early stage of 
life are so soft and tender that they are quite incapable of 
being petrified. Consequently all the petrifactions found in 
the neptunic stratifications of the earth’s crust comprise 
altogether but a very few forms, and of these for the most 
part only isolated fragments. 
We must next bear in mind that the dead bodies of the 
inhabitants of the sea are much more likely to be preserved 
and petrified in the deposits of mud than those of the in- 
habitants of fresh water and of the land. Organisms living 
on land can, as a rule, become petrified only when their 
corpses fall accidentally into the water and are buried at the 
bottom in the hardening layers of mud. But this event 
depends upon very many conditions. We cannot therefore 
be astonished that by far the majority of petrifactions belong 
to organisms which have lived in the sea, and that of the 
inhabitants of the land proportionately only very few are 
preserved in a fossil state. How many contingencies come 
into play here we may infer from the single fact that of 
many fossil mammals, in fact of all the mammals of the 
secondary, or mesozoic epoch, nothing is known except, 
the lower jawbone. This bone is in the first place com: 
paratively solid, and in the second place very easily separates 
