368 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



the American Museum of Natural History, New York, in the order of 

 succession in time as determined by the strata from which the fossils 

 had been taken. One series showed the most gradual and continuous 

 modification in the characters of teeth, another a similarly continuous 

 evolution of horns. 



Again, the well-known fossil Archaeopteryx, found in a series of 

 slates in Germany, would certainly seem to constitute a link between 

 groups now widely separated by divergence in evolution from the 

 same ancestors. This animal is at once a feathered flying reptile 

 and a primitive bird with many reptilian structures. Although 

 Archaeopteryx was a primitive bird, it is in a true sense a "link" 

 between reptiles and the group of modern birds; the gap between 

 these types is filled up by fossil forms like Hesperornis, whose remains 

 are found in strata of a later date. "That these links are not unique 

 is proved by numerous other examples known to science, such as 

 those which connect amphibia and reptiles, ancient reptiles, and 

 primitive mammals, as well as those which come between the differ- 

 ent orders of certain vertebrate classes. The important element in 

 these examples of evolution is, first, their adaptation; secondly, the 

 origination of new parts, and thirdly, the retention of the better 

 invention." 1 Evidence of this kind does not enable us to decide 

 upon the cause of evolution; but in the instances referred to pro- 

 gressive development has occurred gradually, and not by mutation 

 or sudden leaps. 2 On the other hand, they have much to do with 

 the building up of the fittest. As Darwin states: "The tendency 

 to the preservation (owing to the severe struggle for life to which 

 all organic beings at some time or generation are exposed) of any 

 variation in any part, which is of the slightest use or favorable to 

 the life of the individual which has thus varied, together with the 

 tendency to its inheritance. Any variation which was of no use 

 whatever to the individual would not be preserved by the process 

 of natural selection." 3 



Another kind of evidence favoring the idea of the progressive 

 evolution of human beings from simpler orders of animals is the 

 presence of what are known as nonfunctional vestigial structures, 

 relics of past phases of existence, such, for instance, as the unused 

 external muscles of our ears and rudimentary third eyelids; the 

 gill-clefts of reptiles, birds, and mammals, and the hind limbs of 

 whales. The study of these vestigial structures is of importance 

 in showing that ancestral features have great power of hereditary 



i The Doctrine of Evolution, by Prof. H. E. Crampton, p. 99. 

 » E. B. Poulton, The Quarterly Review, July, 1909, p. 18. 



s More Letters, 1. Pp. 126. Quarterly Review, July, 1909, p. 26. Also The Evolution of Living Pur- 

 posive Matter, by N. C Macnamara, vol. 97, International Scientific Series, pp. 2, 53. 



