26 THE ORIGIN OF SPECIES n 



there is assuredly abundant room for him, who, 

 assuming the humbler, though perhaps as useful, 

 office of an interpreter between the " Origin of 

 Species" and the public, contents himself with 

 endeavouring to point out the nature of the prob- 

 lems which it discusses ; to distinguish between 

 the ascertained facts and the theoretical views 

 which it contains ; and finally, to show the extent 

 to which the explanation it offers satisfies the re- 

 quirements of scientific logic. At any rate, it is 

 this office which we purpose to undertake in the 

 following pages. 



It may be safely assumed that our readers have 

 a general conception of the nature of the objects 

 to which the word " species " is applied ; but it 

 has, perhaps, occurred to a few, even to those who 

 are naturalists ex professo, to reflect, that, as com- 

 monly employed, the term has a double sense and 

 denotes two very different orders of relations. 

 When we call a group of animals, or of plants.^ 

 species, we may imply thereby, either that all 

 these animals or plants have some common peculi- 

 arity of form or structure ; or, we may mean that 

 they possess some common functional character. 

 That part of biological science which deals with 

 form and structure is called Morphology that 

 which concerns itself with function, Physiology 

 so that we may conveniently speak of these two 

 senses, or aspects, of " species " the one as mor- 

 phological, the other as physiological. Regarded 



