8 COSMIC PHILOSOPHY. [pt. ii. 



embryology, morpliology, and distribution, and thus fairly to 

 establish the fact that there has been a derivation of higher 

 forms from lower ; and he was also the first to point out 

 the modus operandi of the change. The first of these achieve- 

 ments by itself would have entitled him to associate his name 

 with the development theory; though it was only by the 

 second that the triumph of the theory was practically assured. 

 Just as, in astronomy, the heliocentric theory was not regarded 

 as completely established until the forces which it postulated 

 were explained as identical with forces already known, so the 

 development theory possessed comparatively little value as a 

 working hypothesis so long as it still remained doubtful 

 whether there were any known or knowable causes sufficient 

 to have brought about the phenomena which that theory 

 assumed to have taken place. It was by pointing out ade- 

 quate causes of organic evolution that Mr. Darwiri established 

 the development theory upon a thoroughly scientific basis. 



As Lyell explained all past geologic phenomena as due to 

 the slow action of the same forces which are still in action 

 over the earth's surface and beneath its crust, so Mr. Darwin, 

 in explaining the evolution of higher from lower forms of 

 life, appeals only to agencies which are still visibly in action. 

 Whether species, in a state of nature, are changing or not at 

 the present time, cannot be determined by direct observation, 

 any more than the motion of the hour-hand of a clock could 

 be detected by gazing at it for one second.^ The entire period 



^ " If we imagine mankind to be contemplated by some creature a3 short- 

 lived as an epliemeron, but possessing intelligence like our own — if we 

 imagine such a being studying men and women, during his few hours of life, 

 and speculating as to the mode in which they came into existence ; it is 

 manifest that, reasoning in the usual way, he would suppose each man and 

 woman to have been separately created. No appreciable changes of structure 

 occuiTing during the few hours over which his observations extended, this 

 being would probably infer that no changes of strm'ture were taking place, oi 

 had taken place ; and that from the outset, each man and woman had pos- 

 sessed all the characters then visible — had been originally formed with them. 

 This would naturally be the first impression." — Sioencev, Frinciples 0/ £iology, 

 vol. i p 338. 



