238 



DR. P. CHALMEES MITCHELL ON THE 



unidentified, as the diverticulum is not present, and there is a highly specialized supra- 

 duodenal loop left free by the degeneration of the caeca and closely resembling the 

 duodenum in shape. This similar moulding of the duodenum and the supra-duodenal 

 loop is a condition found in many of the higher forms with relatively short guts. 



ALCID^E. In Fratercula arctica (fig. 57) a conformation of the same general character 

 as that in many of the Gulls appears. The duodenum is of moderate size and not 

 twisted. The greater part of Meckel's tract consists of a set of short loops, the axial 

 of. which bears a large diverticulum in the Ralline position, and of a very large supra- 



Fig. 58. 



Intestinal Tract of Lomvia troile. Lettering as before. 



duodenal loop from which there has not been separated loop " c." Above the vestigial 

 caeca is the curious supra-caecal kink to which attention was drawn in certain Gulls. 

 In Lomvia troile (fig. 58) a Gull-like pattern is displayed. There is no diverticulum to 

 indicate the exact topography. There is a well-formed supra-duodenal loop and a large 

 supra-csecal kink. The caeca are vestigial, and the rectum is extremely short. 



The Laridae and Alcidse are families of birds typically fish-eating, and in which 

 lengthening and narrowing of the gut has to be allowed for. That allowance having 



