INTESTINAI, TKACT OF BIRDS. 2«o 



SwimminGf-birds and most Waders, but that it disappears very early in Birds of I'rey, 

 Parrots, Woodpeckers, and Singini,^-birds. He reu:ards it as a fiinctionless rudiment. 

 Liinnberg and Jagerslviold (21) examined a lari,^' numher of birds, chiefly Sea-birds and 

 Waders, for it, not contentin^• themselves with siiiii'l,> individuals, and found it alisent in 

 most Gulls and Terns, present in Waders. Ducks, llcroMs. and some others. As at an 

 Cfirly stage in my investigations I found it an important jjoint of morphological orien- 

 tation, I searched for it in each of the very lari;e numher of birds upon which this 

 communication is based, and found its presence much more frequent than lias been stated. 

 An interesting feature in connection with it is, that in a large number of cases it is sup- 

 ported by a vestige of the primitive ventral mesentery. Usually this appears only as a small 

 fold of tissue tying down the diverticulum to the ventral edge of tht; sjut, hut sometimes 

 a strong band runs from this towards the liver, the latter of course being develojx'd in 

 the primitive ventral mesentery. Occasionally when the diverticulum itself was absent, 

 its place was indicated l)y the presence of a mesenterial vestige, as in many Pigeons. 



I have found the Divei'ticuknu present and large in all the llatita^ ; of the Colymhifornu's 

 absent only in Pw//Vr/M' ; present in the Spheniscifornu's ; present in the Pi-ocellnriifomies ; 

 of the Ciconiiformes, present and large in all the Steganopodes but small in J-'/ofiiN, and 

 present and larue in the Ardeidte, Scopidie, Ciconiie, and Phcenicopteri, in many of the 

 Ciconiiformes being very large ; present and large in all the Anseriformes ; present in all 

 the Falconiformes (except a Birteoj, and very large in tlie FaIconida% hut usually small 

 in the others ; present and large in the Tinamiformes ; present hnt usually very small in 

 the Galliformes (except Tuniia:); present and very kuire in all f he (Iruiformes, often 

 extremely large, but, as a solitary exception, absent in Ile/iunun ; present and very large 

 in all the Li mi cola? ; among Lari small and olten absent in the Laridae, small, but 

 usually present, in the Alcidae ; present in the Pterocletidte, but usually absent and 

 always extremely small in the Columbida\ a feature in which they stand in marked 

 contrast with the Charadriiformes generally ; of tlu; Cuculiformes, always present 

 although small in the Cuculida? ; absent in the Musophagid*, and probably always 

 absent in the Psittaci ; of the Coraciiformes, always small, but present ratlier more often 

 than not in the Cor;iciie, present and small in most of the Striges, very small but present 

 in most Caprimulgi ; always very small and absent more olten than present in the 

 Cypseli, Colli, Trogones, Pici ; of the Passeriformes, absent in the vast majority of cases, 

 when present extrenudy small except as a solitary case in Menura, where it Avas very 

 large. In making this review I liave exchuled those .specimens which were marked in 

 uiy notes as obviously chicks or quite young birds, and the list may be taken as repre- 

 senting with fair exactness the incidence of the diverticulum among the .A.vian groups. 



In all the eases where I have mentioned, in the paragraph above, that Meckel's diverti- 

 culum Avas small, I think that it was a vestige in the true sense, that is to say a functiouless 

 rudiment of an embryonic structure. !Sometim(^s tJic bunen remained, and contained a 

 few fracments of material resembling volk, and doubtless remains of tlie yolk. Rather 

 more frequently the " small " diverticula had no lumen, ami were mere nodular 

 excrescences on the wall of the 'J'ract. Among the cases which 1 have noted as large there 

 are certainly some (Katites, Palamedeu, etc.) in the same category. 'I"he curious feature 



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