ALIMEXTARV TRACT OF OEIITAIX BrRDS. 49 



Sea-mew, where the spiral is also shown, and it is remarked by the 

 author that the turns of the intestine bear a close resemblance to 

 those of the Crow, Swan, Goose, " Arclea argala,^' &c. — not a verj 

 long series of birds. 



Owen, in describing the Flamingo *, pointed out that the small 

 intestines '' were disposed in twentj'-one elliptical spiral con- 

 volutions, eleven descending towards tiie rectum and ten returning 

 towards the gizzard in the interspaces of the preceding." The 

 same anatomist correctly described the three loops in the small 

 intestine of the Hornbillt. In the 'Comparative Anatomy and 

 Physiology of Vertebrates ' J many more facts are given, most of 

 which appear to be quite correct, but all are not quite intelligible 

 to mj^self. Not many comparisons are made. The Cuckoo 

 is correctly described, but it is not pointed out that it agrees 

 with the Hornbill, which bird, indeed, is not referred to in the 

 volume. The general prevalence of concentric folds among birds 

 with long intestines is noted. The peculiarities of the Galli- 

 naceous birds which have no fixed loops except the duodenal are 

 appreciated in the description of the Common Fowl. The attach- 

 ment of Avhat I term the ileic loop to the gizzard and to the 

 duodenal loop is mentioned. 



Dr. Gadow's contributions § to the subject of the present com- 

 munication have an importance of their own which is very great. 

 But they do not come exactly within the limits of the discussion 

 to which I desire here to contribute, since the aim of that 

 anatomist was to pourtray the arrangement of the gut within the 

 body-cavity and not to delimit only the permanent loops of the 

 intestine as formed upon the supporting mesentery. 



The most recent contributions to the subject known to me are by 

 Dr. Chalmers Mitchell ||. In these memoirs, the author, in addition 

 to discussing some parts of the subject with which I am not 

 concerned here, deals with a much larger series of species than 

 any previous author and has arranged his observations systema- 

 tically, so as to cover most of the existing groups of birds. His 

 special object, however, was to trace the various modifications of 

 the intestinal tract to what he believed to be a primitive type, to 

 arrange them in the form of a phylogenetic tree, and to see how far 

 such a tree would agree with or correct conceptions of the phylo- 

 genetic ideas regarding birds as a whole. In the course of this 

 paper I shall refer to vai'ious points in which my own observa- 

 tions do not agree with those of Dr. Mitchell. In my opinion, 

 however, Dr. Mitchell's mode of figuring the intestinal tract of 

 birds gives an aj^pearance of simplicity which is misleading, with 

 the result that birds which are separated by marked characters 



* P. Z. S. 1832, p. 142. t Ihid. 1833, p. 102. 



+ Vol. ii. 1866, p. 167 et seq. 



§ " Vergl. Anatomie des Vevdauungssystemes der Vogel," Jen. Zeit.'sclir. 1881. 

 "On the Taxonouiic Value of the Intestinal Convolutions in Birds," P. Z. S. 

 1889, p. 305 ; iu Newton's ' Dictionai-y of Birds,' suh voce " Digestive Sy.stem." 



II "On the Intestinal Tract of Birds, Ac," Trans. Linn. Soc. viii. 1903, p. 175; 

 and an earlier paper in P. Z. S. 1396, p. 136. 



Proo. Zool. Soc— 1911, No. lY. 4 



