210 



1)K. P. CHALMERS MITCHELL ON THE 



of the system can*ying a Meckel's diverticulum. There is a well-formed supra-duodenal 

 loop, flhich is spirally twisted, and a large supra-csecal kink has a similar arrangement- 

 I'lie cac^ca are vestigial, and the rectum is short and straight. Saliaetus leucogaster 

 differs from the foregoing only in that its duodenum is spirally twisted. These two 

 birds are large and chiefly piscivorous, and the homojilastic increase in gut-length has 

 obscured the peculiar cliaracters of the Falconiform gut, but the general symmetry, the 

 peculiar duodenums, and the well-formed supra-caecal kinks are sufficiently distinctive. 

 The other Aquilinae repeat exactly the pattern displayed by Circus, the only slight 

 n^.odification I have found being that the supra-duodenal looji in Spiza'etus, although 

 (iniined by a " bridging "' vein, is very small. The sujjra-caecal kink is very large in 

 most and distinct in all. 



(5) Buteoitiitce. — Of these I have examined Astur ladiiro, Asturlna magnirostris, 

 Buieo efythronotiis, JB.ferox, B.jucal, Jlilvus gomnda, M. iciinus, M. migrans. In all 

 the pattern of Circus is reproduced with close fidelity. The duodenum is irregular, 

 sometimes long, narrow, and straight as in the genus Buteo, sometimes irregularly 

 expanded, or folded upon itself several times as in some species of Jlilvus. Meckel's 

 tract is always as in Circus, save that in a Buteo no trace of Meckel's diverticulum was 

 retained. The supra-duodenal fold is always pi'esent as also is a large supra-caecal kink. 

 The caL'ca are vestigial and the rectum is short and straight. 



(6) Faiconince. — I have examined Falco concolor, F. Feldeggi, F. lanarius, F. mela- 

 iiogeiiys, F. jjeregriiius, and Microhierax melauoleucus. The Falconinaj certainly exhibit 



Fig. 32. 



Intestinal Tinct of Falco iiielanor/enyg. 

 ?'.»!., vise-oral nervc--fhain. Lettering; as before. 



the most specialized or apoccntric form of gut among the rakcmidse. The duodenum i.s 

 always a large irregular loop, sometimes with minor folds (fig. 32), sometimes bent on 

 it-self (fig. 33). Meckel's tract is always very much elongated in the axial line, and 



