192 



DR. P. CHALMERS MITCHELL ON THE 



long loop, at the end of which lay what I took to have heen a Meckel's diverticulum. 

 Then follows a very long posterior portion, relatively longer than in the diagram, and 

 thrown into a series of straight minor folds, the posterior of which is a supra-duodenal 

 loop with a " bridging " vein. Just beyond this is the trace of a supra-csecal kink. The 

 rectum is long and wide, in fact is typically archecentric. Of the usual pair of caeca, 

 only one was developed, and that in a vestigial form, but Beddard (2) states that indi- 

 viduals vary, some possessing two vestiges. The minor loops of Meckel's tract show a 



Fig. 13. 



m .' 



Intestinal Tract of Plotus anhinga. 

 C.C., single colic caecum ; k ?, possible supra-ciecal kink ; m ?, possible position of Meckel's diverticulum. 



tendency to be bunched up as in the Pelicans. If I were wrong in my placing of 

 Meckel's diverticulum, and what I took for it was the merest trace, the character of the 

 gut would not be so unlike that found in the Cormorant ; but in any event the differences 

 between the two forms are wide, and make it plain that if other characters justify the 

 inclusion of Plotus among the Phalacrocoracidae, the association is by no means close. 

 On the evidence of the intestinal tract I should be inclined to place Plotus in a separate 

 family. 



(4) FREGATIDJ-E. In Fregata (fig. 14) the form of the intestinal tract is very like 

 that displayed by Phaethon. The chief differences are that in Fregata the whole tract is 



