120 CHAPTERS ON EVOLUTION. 



that " morphology plainly tells us that our lungs consist of a modified 

 swim-bladder which once served as a float ; " and again : " According 

 to this view, it may be inferred that all vertebrate animals with true 

 lungs are descended by ordinary generation from an ancient and 

 unknown prototype, which was furnished with a floating-apparatus 

 or swim-bladder." 



The discussion of biological odds and ends has thus brought us 

 face to face with that great problem of nature the origin of species 

 which admits of a fair and rational solution only on the hypothesis 

 that change, alteration, and modification in living beings perpetuated 

 by descent, and favoured or annulled by the action of "natural selec- 

 tion," constitute the factors which are responsible for the existing 

 order of things. The most abstruse phenomena of nature and the 

 most diverse facts of life, are brought by this theory into definite 

 relationship, and made to serve as pathways towards the knowledge 

 of still hidden laws. Under the old regime, in which the operation 

 of a special creative force, alike erratic in its action and spasmodic 

 in its work, was made to do duty as the originative method of this 

 world and its belongings, the universe itself was simply a connection 

 of paradoxes and insoluble enigmas. The naturalist of bygone days 

 had need for a full cultivation of unreasoning faith in this unknown 

 creative method; since of its apparent vagaries he was unable to 

 give any rational account. Now, with the theory of evolution at 

 hand, the disconnected facts of natural history fall into an harmo- 

 nious and unbroken sequence of finger-posts and guides, pointing 

 the way of creation as having passed through the pathways of 

 descent, with modification as its henchman, and adaptation to new 

 ways of life as its "guide, counsellor, and friend." 



