INTESTINAL TRACT OF PENGUINS. 



21 



nately my material has been restricted to nestlings only. Nevertheless it seems to me 

 that the peculiarities in the tracts in question are too marked to be materially affected 

 by age. Dr. Chalmers Mitchell has shown that Catarrhactes, Spheniscus and Apteno- 

 dytes agree rather closely one with another in the great length of Meckel's tract, and 

 in the form of the supra-duodenal loop, which is simple and in all of considerable 

 length relatively longest in Spheniscus and shortest in Eudyptes. Spheniscus and 

 Catarrhactes alike have the duodenal loop of great length and thrown into a series of 

 minor loops, wherein they differ from Aptenodytes, in which the duodenal loop is simple, 

 of great length, and coiled upon itself. 



It would now appear, from what follows, that while among the penguins there is 

 to be found a common general 

 resemblance in the convolu- 

 tions of this tract, there is, at 

 the same time, a greater range 

 of differences between the 

 species of a genus than might 

 have been supposed ; how 

 great this range may be is a 

 matter for further research. 



Thus, while in the King Pen- 

 guin, A. patagonica, the duo- 

 denal loop is a simple closed 

 loop coiled upon itself ; in 

 the Emperor, A. forsteri, it 

 forms what may best be 

 described perhaps as a series 

 of interlocking U-shaped loops 



FIG. 7. THE INTESTINAL TRACT OP A NESTLING PygoSCellS adellK. 



Note the coiled duodenal loop. 



(fig. 6) ; while in the Adelie 

 Penguin, Pygoscelis adelise, 

 the loop is, as in the King Penguin, simple and coiled, but the coils, however, are 

 much more voluminous, as may be seen in fig. 7. The Adelie and Emperor Penguins 

 show a further common resemblance in that in both species the supraduodenal loop is 

 folded back upon itself instead of forming a single loop as in the other genera already 

 described : while the tract in Pygoscelis is still further remarkable in that the loops in 

 Meckel's tract appear to be fewer in number than in any other penguin yet ex- 

 amined, though it must be remembered that the condition here described is that of a 

 nestling. The number of loops may increase with age. 



Meckel's diverticulum in the young Emperor Penguin is situated, not as usual at 

 or near the end of the apex of a loop, but at the bottom of the valley between two 

 adjacent loops (fig. 8). 



The very remarkable difference displayed by the intestinal tracts of the King and 



