238 THE REIGN OF LAW. 



strengthened by some of the facts which we dis- 

 cover when we examine and compare with each 

 other the genera and species of which it is com- 

 posed. There is a beautiful gradation between 

 the different genera and the different species, — so 

 much so, that it has been found impossible to 

 divide the Humming Birds into more than two 

 sub-families, from the absence of sufficiently well- 

 marked divisions. And yet, on the other hand, 

 they cannot be arranged in anything like a con- 

 tinuous series, because some links appear to be 

 missing in' the chain. 



But these general facts terminate in nothing 

 more definite than a vague surmise. When we 

 enter farther into details, we feel at once how little 

 they agree with any physical law which is known 

 or even conceivable by us. If the likeness which 

 prevails in the whole group reminds us of the 

 likeness which is due to community of blood, it 

 is equally true that the differences between the 

 species are totally distinct both in kind and de- 

 gree from the variation which we ever see arising 

 among the offspring of the same parents. Let us 

 look at what these differences are. The generic 



