ALIMENTARY TRACT OF OERTAIX BIRDS. 89 



precisely similar so far to that of the Gallinaceous birds. We 

 have in certain Picopasseres (e. g., Melanerjyes) the same state of 

 aft'airs, coupled in this case with a considerable shortening of the 

 gut. Among the Limicolae the genus Pltcvianus is also in this 

 stage. 



The next stage, which may be called Stage B, is like the last, 

 save for the fact that the ileic loop is definitely formed. The 

 jejunal region remains unspecialised. To this stage, we refer the 

 gut in the majority of Picopasseres, including the Cuckoos and 

 Plantain -eaters. The "Alectorides" (in the sense in which I ventui^e 

 to use that term in the present communica,tion) seem, but perhaps 

 only seem, to belong to this stage. Among the Limicolous birds 

 iSa?'ciophoi-}ts find Gulls appear to belong here. Perhaps we should 

 also place in this assemblage the Dyspor-omorph Fregata. 



Stage C is a slight advance upon the foregoing. It is exem- 

 plified in certain Owls and Hawks, where the ileic loop is fully 

 difi"erentiated off and attached in the usual way to the duodenum, 

 and where the jejunum is largely laxly coiled without any definite 

 loops, save a single loop, and that not a very well-marked one, 

 which occui-s at the commencement of the jejunum. I have not 

 noticed this kind of intestine in any other group, except the 

 Nocturnal and Diurnal Birds of Prey. 



Stage D might possibly be further divided up, but for the 

 present I do not see a clear Way through the great variations 

 which the intestine of the more complicated forms shows. In all 

 of them the jejunum has become differentiated into fixed loops, 

 which vary in number, in relative length, and in their relations 

 one to the other. The majority of the larger birds belong to this 

 stage, as, for instance, the Cranes, Rails, Ducks, and Storks. 



§ TJte Mutual Affinities of Avian Families jicctged hy the 

 hitestinal Coiivohitiovs^ 



The known facts do not, a«s I think, permit of any complete 

 scheme of classification of Birds by means of the variations in 

 the coils of the intestinal tract. Here and there, however, there 

 would seem to be such indications, which are tolerably well 

 marked. More frequently, however, either a general plan runs 

 through a seiies of two or three groups, which makes any 

 definite placing of these groups in reference to each other 

 difiicult, oi" a complete isolation is shown. The most salient 

 instance of the latter conclusion is undOTibtedlj' the group of 

 Parrots, whose intestinal coils are constructed upon a. plan which 

 is apparently universal in that group, but totally unlike anything 

 which i&' to be found in any other group. The afiinities of the 

 Psittaci have been very variously interpreted *, but it is clear 

 that the gut does not enable one to decide upon any of these 

 divei'se views.- I cannot at all agree with Dr. Mitchell in saying 



* Miuij- or most of tlicse ojiiiiions arc mentioned by Fiirlirin<rcr in liis 

 monumeiita'l' worlc. ' Uii'tursuehuimcn neber Morpli. ii. ^yst. dev Vogcl,' Amsterdam, 

 1888. 



