INCOMPLETENESS OF THE BIOLOGICAL RECORDS. 39 



an imperfect knowledge in this department. It must be 

 lemembered, that far the greater proportion of the rock 

 ■sti-afca which constitute the mountain masses of the surface 

 of the earth is not yet unfolded to us. Of the count- 

 less petrifications which are hidden in the huge moun- 

 tain chains of Asia and Africa, we kno'.v but a few small 

 samples. Part of Europe and of North America has alone 

 been more minutely explored. The wdiole of the petri- 

 factions accurately known and in our collections do not 

 amount to a hundredth part of those which really exist in 

 the crust of the earth. In this respect we may, therefore, 

 expect a rich harvest of discoveries in the future. But, in 

 spite of this, the pahBontological record of creation (for 

 reasons which I have amply explained in Cliapter XV. ot 

 my "Natural History of Creation") will alw^ays renin in 

 extremely incomplete. 



Not less incomplete is the second, most important recuid 

 of creation, that of Ontogeny. For the Pljylogeny of the 

 individual it is the most important of all. Yet, it also has 

 its great defects, and often leaves us in the larch. In this 

 matter, we must distinguish quite clearly between palin- 

 genetic and kenogenetic phenomena, between the original, 

 inherited evolution and the later, vitiated evolution. We 

 must never fori^et that the laws of abridiied and vitiated 

 heredity frequently disguise the original course of evolution 

 beyond recognition.. The reproduction of the Phylogeny 

 in the Ontogeny is but rarely tolerably complete. The 

 earliest and most important stages of germ-history are 

 usually the most abridged and compressed. The youthful 

 evolutionary forms have in turn often adapted themselves 

 to new conditions, and have thus been modified. The 



