CHAPTER VI. 



SPECIES AND TIME. 



Two relations of species to time. No evidence of past existence of minutely 

 graduated intermediate forms when such might be expected a priori. 

 Bats, Pterodactyles, Dinosauria, and Birds. Ichthyosauria, Chelonia, 

 and Anoura. Horse ancestry. Labyrinthodonts and Trilobites. Two 

 subdivisions of the second relation of species to time. Sir Wm. Thom- 

 son's views. Probable period required for ultimate specific evolution 

 from primitive ancestral forms. Geometrical increase of time required 

 for rapidly multiplying increase of structural differences. Proboscis 

 monkey. Time required for deposition of strata necessary for Dar- 

 winian evolution. High organization of Silurian forms of life. 

 Absence of fossils in oldest rocks. Summary and conclusion. 



Two considerations present themselves with regard to the 

 necessary relation of species to time, if the theory of 

 " Natural Selection " is valid and sufficient. 



The first is with regard to the evidences of the past 

 existence of intermediate forms, their duration and suc- 

 cession. 



The second is with regard to the total amount of time 

 required for the evolution of all organic forms from a few 

 original ones, and the bearing of other sciences on this 

 question of time. 



As to the first consideration, evidence is as yet against 

 the modification of species by " Natural Selection " alone, 

 because not only are minutely transitional forms generally 



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