166 STRUCTURE AJSfD CLASSIFICATION OF BIRDS 



I have italicised in the above Hst those groups which 

 come near to the supposed primitive condition ; and it will 

 be observed that those groups which are italicised are enough 

 to account for the ancestry of the rest. The main difficulty 

 is perhaps presented by the Cuculi ; but it may well be that . 

 that group will ultimately prove to have a simple intestinal 

 tract. It will be observed also that the groups in question; , 

 comprise representatives of all the five large divisions of 

 existing birds admitted by Gadow, and of all the corre-' 

 spondingly large divisions of Fuebbingbr. Incidentally, 

 therefore, I find myself in reassuring agreement with those 

 authorities. In the systematic part of this work I have to 

 some extent discussed the mutual affinities of these different 

 groups. 



