12 Introduction. 



matter of course by the true conception of that which had been 

 hitherto figuratively called affinity ; the degrees of affinity ex- 

 pressed in the natural system indicated the different degrees of 

 derivation of the varying progeny of common parents ; out of 

 affinity taken in a figurative sense arose a real blood-relation- 

 ship, and the natural system became a table of the pedigree of 

 the vegetable kingdom. Here was the solution of the ancient 

 problem. 



Darwin's theory has this special interest in the history of the 

 science, that it established clearness in the place of obscurity, 

 a scientific principle in place of a scholastic mode of thought, 

 in the domain of systematic botany and morphology. Yet 

 Darwin did not effect this change in opposition to the historical 

 development of our science or independently of it ; on the 

 contrary his great merit is that he has correctly appreciated the 

 problems long existing in systematic botany and morphology 

 from the point of view of modern research, and has solved 

 them. 



That the constancy of species is incompatible with the idea 

 of affinity, that the morphological (genetic) nature of organs 

 does not proceed on parallel lines with their physiological and 

 functional significance, are facts which were known in botany 

 and zoology before the time of Darwin ; but he was the first to 

 show, that variation and natural selection in the struggle for 

 existence solve these problems, and enable us to conceive of 

 these facts as the necessary effects of known causes ; it is at 

 the same time explained, why the natural affinity first recog- 

 nised by de 1'Obel and Kaspar Bauhin cannot be exhibited by 

 the use of predetermined principles of classification, as was 

 attempted by Cesalpino. 



