ORIGIN OF ORGANIC FORMS 321 



Darwin, can offer in explanation of the perfection and 

 harmony of the organic world. Let us cast a glance 

 back over what we have said on the subject. If we are 

 able to analyse the majority of vital phenomena into 

 their simplest physico-chemical principles, and can 

 explain them by causes now at work, we are nevertheless 

 obliged to go back to historical causes in order to explain 

 all that concerns adaptation. In order to explain the 

 perfection of organisms by this method, we must begin by 

 proving that they actually have a history, and then that 

 this historical development tends towards perfection. 

 The united testimony of all the branches of biological 

 science, of classification, comparative morphology, 

 embryology, palaeontology, goes to prove the common 

 origin of organic forms. The only objection to this 

 theory is the belief in the immutability of specific 

 forms ; but the criticism of the very conception of 

 species, and moreover certain facts with regard to 

 domesticated animals, which have been established with- 

 in the limits of human memory, remove this objection. 

 Having proved that all the facts speak in favour of, 

 and nothing against, the conclusion that the organic 

 world has a history, we studied the veiy nature of 

 this historical process. Starting from such obvious 

 properties of all organisms as variability, heredity, 

 and the rapid rate of multiplication; we came to the 

 conclusion that this historical process inevitably leads 

 an organism towards perfection, through what Darwin 

 rightly called ' natural selection.' His theory does not 

 therefore give any ready explanation of the existence of 

 this or that special form, of this or that particular case ; 

 it indicates the general method by which this explanation 

 may be arrived at in any given case. If we are able to 

 discover the original cause of variation, and farther to 

 indicate the continuous series of transitional forms (as 

 we tried to do in the case of the sage) , the origin of the 

 most complicated form, provided it be useful to the 



X 



