276 THE ORIGIN AND EVOLUTION OF LIFE 



acter. Sometimes a character lags behind and through failure 

 to keep pace produces the dysteleogy or imperfect fitness of 

 certain parts of the organism observed by Metchnikoff in the 

 human body. 



Sometimes there are serial regiments of such well-ordered 

 characters which are exactly or closely alike — for example, 

 the 1092 teeth in the upper jaw of the iguanodont dinosaur, 

 Trachodon, all very similar in appearance, all evolving and all 

 perfectly coordinated in form and function with the 910 teeth 

 in the lower jaw of the same animal. There are other serial 

 regiments of characters, however, like the vertebrae in the 

 backbone of a large dinosaur, for example, in which every 

 single character, large and small, is different in form from 

 every other. These are among the many miracles of adapta- 

 tion referred to in the Preface. 



The evidence for this continuous and more or less adaptive 

 direction in the simultaneous evolution of numberless char- 

 acters which can be observed only by means of an ancestral 

 fossil series was unknown to the master mind of Darwin 

 during the preparation of his "Origin of Species" through 

 his observations on the variations of domestic animals and 

 plants between 1845 ^^'^ 18585 ^oi" it was not until the dis- 

 covery by Waagen, in 1869, of a continuous series of fossil 

 ammonites, in which minute changes originate and can be 

 followed continuously, that the rudiment^ of a true concep- 

 tion of the orderly and continuous modes of evolution which 

 prevail in nature were reached. Among invertebrates and 

 vertebrates, this conception has been abundantly confirmed 

 by modern palaeontology in all its branches, namely, that 

 of a well-ordered continuity as the prevailing mode of evolu- 

 tion. This is the greatest contribution which palaeontology 

 has made to biology and to natural philosophy. 



