Anatomy of the Kingfishers. 103 



themselves to an arrangement in a graded series^ which 

 suggests the production of one condition as a simple modifi- 

 cation of the other. At one end of such a series stand Dacelo 

 and Sauropatis, diastataxic in the strictest sense, there being a 

 wide gap in the quill series, and this gap, with the exception 

 of the quill, being occupied by a complete diagonal row. 

 Next come Ceryle maaima and C. aIcyon,&U\\ diastataxic but 

 with the width of the gap much reduced. Then comes 

 Halcyon pi/eata, eutaxic, without a gap, but with a possible 

 remnant of the other condition in the form of a reduced 

 diagonal row of three small feathers. Then come the other 

 eutaxic forms with no gap and no trace of the diastataxic 

 diagonal row. In my paper on the wings of the Columbidse 

 I advanced an hypothesis that the diastataxic condition was 

 primitive, and suggested a mode in which it might have 

 arisen. Without for the present recurring to that suggested 

 origin, I am content to point out that were the wings of all 

 birds originally diastataxic it is not difficult to see that by 

 closing of the gap, and consequent gradual obliteration of 

 the row that occupied the gap, the eutaxic condition might 

 have been produced. Moi cover, if the production of eutaxy 

 be part of a general process of the formation of a simpler 

 but more specialized organ of flight from an older and more 

 diffusely arranged organ, there is no theoretical difficulty iu 

 supposing it to have been produced separately and inde- 

 pendently in many different kinds of birds. On the other 

 hand, if so remarkable an arrangement as the absence of a 

 single quill, in a definite and identical position, has been 

 pioduced from a primitive eutaxy, we have either to make 

 the supposition that all the diastataxic forms are more closely 

 related to each other than to the eutaxic forms — a suggestion 

 that strikes rudely across all natural classifications — or to 

 face the almost impossible idea of its polyphyletic origin. 

 I will now proceed to review the anatomical fi;cts "men serve 

 to show that the eutaxic Kingfishers are in other respeccs the 

 more specialized birds. 



There is not much information to be derived from tne 

 geographical distribution and external characters of the 



