. Natural history. Geology; Zoology; Botany. 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
. Natural history. Geology; Zoology; Botany. 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. 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
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