INTEODUCTION. 



I HAVE first to express to the Trustees of the British Museum, and to 

 all Ornithologists, my regret for the delay which has occurred in finishing 

 this fifth volume of the 'Hand-list.' The work was commenced in 1898, 

 and the first volume published in 1899 : it has, therefore, occupied ten 

 years in completion. Although the whole of it had to be written in 

 my private time, I imagined that five years would have been ample to 

 finish the book, being at the rate of one volume every year. The 

 increased number of students in the Bird-Section of the Museum has 

 taken up so much of my official time, that my private time has been 

 largely occupied with Museum correspondence, and recently I have 

 seldom been able to find any leisure wherein to write the ' Hand-list.' 



Some exception has been taken to my recognition, as species, of all 

 the forms described as sub-species, or races with trinomial names. My 

 views on this subject have often been stated, and as for trinomials, 

 I look upon the system as destructive. I consider that the burden 

 imposed upon the Zoologists who follow this method for the naming of 

 tlieir specimens will become too heavy, and 'the system will fall by its 

 own weight. That races or sub-species of birds exist in nature, no one 

 can deny, but, to my mind, a binominal title answers every purpose, 

 and a system of nomenclature which calls the Hawfinch, Coceothraustes 

 coccoihravstes coceothraustes, and the Common Swift, Apus apus apus, will 



