BR. DRAPER'S LECTURE ON EVOLUTION. 187 



existing ones. In the Secondary, reptiles, and out of them birds, were 

 developed ; the decreasing amount of carbonic acid and the increas- 

 ing amount of oxygen permitting that change. Of birds, the earli- 

 est had a long, lizard-like tail, composed of thin vertebrae, to every 

 one of which were attached strong, rudder-like feathers in pairs. The 

 same formation of the tail part of the vertebral column still occurs 

 transiently in the embryos of later birds. The transition from the 

 reptile to the bird is manifested by some of the latter having teeth 

 set in one order in grooves, in another in distinct sockets. Among 

 mammals as among fishes the imperfect appeared first. About the 

 middle of the Mesolithic period, out of a branch of the cloacal animals 

 the marsupials were evolved ; and in the beginning of the Tertiary 

 the placentals were developed out of the marsupials. The latter were 

 at one time distributed over the whole earth ; now they are fast 

 approaching extinction. In Europe, Asia, Africa, not a single mem- 

 ber of the group remains. The cloacal animals, the marsupials, the 

 placentals, stand therefore in an order of succession. 



Such has been the order of evolution in Europe. For its order in 

 America I may refer you to the recent admirable address of Prof. 

 Marsh before the American Association for the Advancement of Sci- 

 ence. The general conclusions at which we arrive in one case are 

 substantiated in the other. 



In accordance with his descent, the cloacal structure exists in 

 man in the earlier period of his embryonic life. The separation into 

 two openings takes place about the twelfth week of his uterine de- 

 velopment. Shall we not, therefore, infer from the evidence of his 

 embryonic forms that he has been developed step by step out of the 

 lower vertebrates ? 



In the early stages of their evolution, amphibia, reptiles, birds, 

 cannot be distinguished. The first steps of development in all verte- 

 brates are identical. Man passes now through the same series of 

 transmutations which his animal predecessors passed through in im- 

 mense spaces of time, long ago. The progress he makes in the lapse 

 of a few days in the darkness of the womb is the same that has been 

 followed by the procession of animated Nature in the lapse of myri- 

 ads of centuries in the daylight of the world. 



From a comparison of their studies embryologists and paleontol- 

 ogists unite in the conclusion that individual development is a rapid 

 repetition of race-development, and that the paleontological move- 

 ment is to be interpreted by the embryonic. The connecting links 

 supposed to be missing in the former may be sought for in the latter. 

 Individual development, paleontological development, and compara- 

 tive anatomy, through their combined evidence guide us to a deduc- 

 tion of the genealogy of any organism. The dominion of law is 

 everywhere manifest. The capricious intrusion of a supernatural 

 agency has never yet occurred. 



