Introduction. 1 1 



suggested objections to such views, these objections were 

 usually little regarded, and in fact reflections of this kind 

 on the real meaning of the natural system did not often 

 make their appearance ; the most intelligent men turned 

 away with an uncomfortable feeling from these doubts and 

 difficulties, and preferred to devote their time and powers 

 to the discovery of affinities in individual forms. At 

 the same time it was well understood that the question 

 was one which lay at the foundation of the science. At 

 a later period the researches of Nageli and others in mor- 

 phology resulted in discoveries of the greatest importance to 

 systematic botany, and disclosed facts which were necessarily 

 fatal to the hypothesis, that every group in the system represents 

 an idea in the Platonic sense ; such for instance were the re- 

 markable embryological relations, which Hofmeister discovered 

 in 185 1, between Angiosperms, Gymnosperms, Vascular Crypto- 

 gams and Muscineae; nor was it easy to reconcile the fact, 

 that the physiologico-biological peculiarities on the one hand 

 and the morphological and systematic characters on the other 

 are commonly quite independent of one another, with the plan 

 of creation as conceived by the systematists. Thus an oppo- 

 sition between true scientific research and the theoretical views 

 of the systematists became more and more apparent, and no 

 one who paid attention to both could avoid a painful feeling of 

 uncertainty with respect to this portion of the science. This 

 feeling was due to the dogma of the constancy of species, and 

 to the consequent impossibility of giving a scientific definition 

 of the idea of affinity. 



This state of things finally ceased with the appearance of 

 Darwin's first and best book on the origin of species in 1859 ; 

 from a multitude of facts, some new, but most of them long 

 well-known, he showed that the constancy of species was no 

 longer an open question ; that the doctrine was no result of 

 exact observation, but an article of faith opposed to observa- 

 tion. The establishment of this truth was followed almost as a 



