124 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



ments du Monde Animal. Finally, von Zittel synthe- 

 sized with admirable exactness the important general 

 facts which, from the end of the nineteenth century 

 onward, could be disentangled from the enormous 

 and growing mass of palseontological materials, 

 and slowly led our science toward the discovery of 

 its principles and of its laws. 



At the present moment it would be rash to 

 affirm that we know satisfactorily the general law 

 which has presided over the unceasing transforma- 

 tion of beings from the apparition of life down to 

 our existing world. Neither the mechanism of 

 physiological adaptations, nor that of the direct 

 action of the surroundings, nor, still less, that of 

 the struggle for life, are adequate to furnish a 

 rational and complete explanation of the mag- 

 nificent picture of palseontological evolution. There 

 still exist in this evolution, without even mentioning 

 the first origin of life, many mysterious points and 

 important facts, explanations, of which escape us. 



But if we can make up our minds to abandon in 

 future this general and theoretical side of evolution, it 

 will be possible, as a compensation, to settle exactly 

 a certain number of laws of detail, or, more exactly, 

 of frequent repetitions of the same facts, which, if they 

 have not the absolute value of the great physical 

 or mathematical laws, present none the less a philo- 

 sophical interest of the highest order, and throw 

 thenceforth a strong light on the natural process of 

 the transformation of early beings. 



I propose to set forth and discuss, in the following 

 chapters, those of these palceontological laws which 

 seem best established. 



