.THE 



CLASSIFICATION OF BIRDS 



THE following attempt at a natural classification of Birds is based 

 upon the theory of Evolution. It assumes that all Birds are 

 descended from one original species, whose early history is lost in 

 the imperfection of the geological record, but which had become 

 differentiated into many widely varying species as long ago as the 

 Cretaceous Period. It is not necessary to adopt any particular 

 theory of Evolution. The fashionable opinion at the present 

 moment appears to be in favour of Weismann's hypothesis that 

 the sole machinery of Evolution is the Natural Selection, by means 

 of the Survival of the Fittest, of those individuals who are for- 

 tunate enough to be born with some fortuitous variation which 

 is advantageous to themselves and can be transmitted to their 

 offspring. More conservative ornithologists are disposed to narrow 

 rather than widen the part played by Natural Selection, and to 

 agree with the great author of the " Origin of Species " when he 

 wrote to Moritz Wagner : " In my opinion the greatest error 

 which I have committed has been not allowing sufficient weight 

 to the direct action of the environment i.e., food, climate, &c. 

 independently of Natural Selection " (" Life and Letters of Charles 

 Darwin," iii. p. 159). The hypothesis that the _ tendency of 

 organisms to develop in a definite direction is a primitive char- 

 acter with which Life was already endowed when it first made its 

 appearance in the dead world of Matter and Force, which reigned 

 supreme on our planet for countless ages, is still the only plausible 

 explanation of many of the facts of Evolution. 



The theory of Evolution in general, or the hypothesis of 

 Natural Selection in particular, makes a large demand upon our 

 faith. It crumbles away if it be approached in- an agnostic spirit. 

 It satisfactorily explains a great many facts, but it leaves a great 



