8 INTRODUCTION. 



(Archseopteryx) and the most bird-like reptile 

 (Compsognathus). 



In the vegetable kingdom, no connecting link 

 has been found between the two classes of Vascu- 

 lar Cryptogams; Equisetacese and Ferns. 



The longer a type is in existence the more it will 

 deviate from the ancestral form ; variations become 

 species ; species develop generic differences, till 

 finally the originally homogeneous type splits into 

 several series of forms, so differentiated by pecu- 

 liarities developed in the course of ages that they 

 must be considered families and orders. This pro- 

 cess takes place by the individuals adapting them- 

 selves to external conditions, brought on by grad- 

 ual geological changes, and it is astonishing what 

 a variety of differences can grow out of the same 

 old stock. All the immense variety of organic life 

 must be ascribed to the repetition, or rather the 

 continuation of this process. 



The original type exists after a time, only in 

 modifications caused by adaptation to new circum- 

 stances, which modifications from the same cause 

 will also divide, and so indefinitely, because in this 

 world changes are constantly going on. There is 

 neither pause nor return. The Creator never re- 

 peats himself. 



The ancestral types, the skeletons and other 

 traces of which are known only in the fossil state, 

 are said to be extinct, and in some cases they really 

 are so. They succumbed in the battle for exist- 

 ence, and were destroyed. This has often taken 



