256 



DE. P. CHALMEKS MITCHELL ON THE 



SUMMAKT OF THE CORACIOMOKPHINE LeGION. (Plate 23.) 



Gadow (12) unites the Cuciiliformes, Coraciiformes, and Passeriformes into the 

 Coraciomorphae, the second legion of his second Brigade. The simplest and apparently 

 most archecentric type of intestinal tract to be found among these birds occurs in the 

 Caprimidgi. This, which I call the Coraciomorphine metacentre, is a simple derivative 

 of the archecentric type, and is changed from that practically only in the shortness and 

 straightness of the rectum, although the duodenum tends to be rather wider relatively. 

 Prom this metacentre the Passerine gut is a very apocentric derivative, the changes 



Fig. 74. 



Passeres 



Psittaci Ak 



Upupid^ 



cedmi 



Meropidas 



Cuculidae 



CoraciforiD 

 Cuculiform 

 Metacentre 



Caprimulgi 



Coracimorphme 

 Metacentre 



Palamedea 

 Archecentre 



Evolution of tho Intestiual Tract of the C'oraciomor])hine Legion. 

 (For C'oracimorphiue read Coraciomorphine.) 



being the specialization of Meckel's tract into a proximal portion which bears the 

 diverticulum, and which is wound into a long or short spiral, and a distal portion 

 which is an extremely specialized supra-duodenal loop. The cfeca have also been 

 reduced in size. The conformation of the Cypseli and Colii may also be an apocentric 

 derivative of the Caprimulgid form, the apocentricity in both consisting of an immense 

 reduction in the length of the whole gvit, with degeneration of the cseca so that no 

 vestige of them is left, and with obliteration of the loops in Meckel's tract ; there may 

 or may not be a supra-duodenal loop. The Coraciidse present a less apocentric moditi- 



