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Show 344 ON THE ANATOMY OF PLOTUS ANHINGA. [Apr. *L tissue of the corium, which occupies the intermediate space, is very small in amount. Between the tissue and the hair-root is seen a layer of columnar epithelium cells, which in some places are of considerable ' length. They are continuous towards the surface with the deeper cells of the stratified epithelium. They represent the 'root-sheaths ' of the cutaneous hair, and seem to have undergone a horny metamorphosis. " At their extreme ends the roots are entirely different from those of the cutaneous hairs. There is no hair-knob and no papilla ; but the root generally breaks up into two, three, or more short rootlets, each of which tapers to a pointed extremity. This, at least, is the appearance in vertical section ; but transverse sections show that this branching of the hair-root has, at all events in the first instance, more of a laminated character. " These rootlets are covered by a layer of cubical epithelium cells, which are continuous with the columnar cells surrounding the hair-root. The latter, as before remarked, is formed merely by the fibrous substance or cortical portion of the hair; and the fibres which compose this would therefore seem to be in some way produced by these cells. " Some few hairs seem to end by a single tapering rootlet, but most of them spread out and branch in the way described." This peculiar hairy mat must act as an excellent sieve to prevent the entrance of solid particles, fish-bones, ckc. into the narrow intestines. The small intestine is 55 inches long in the female, and 40 inches in the male ; and it is not capacious. The duodenal loop measures 5 inches in each limb. The left lobe of the bilobed liver is about half the size of the right; and a gall-bladder of considerable size is present, The large intestine is 6 inches long in the female, and 3 inches in the male. There is only a single caecum, exactly like that in the Ardeidae, in m y specimens. This conformation of caecum is found in no other Steganopod bird, there being two caeca in all the other genera. These, in Pelecanus, are a little over an inch in length, in Sula slightly shorter, whilst in Phalacrocorax, Fregata, and Phaethon they are simple knob-like bodies, nearly globose in form. The rudiment of the vitelline duct is persistent. In the distance of its diminutive caecum from the cloaca (in other words, in the length of the large intestine) Plotus differs slightly from its allies. In Pelecanus the large intestine is under 2 inches in length ; and it is much the same in Sula. In Phaethon it does not exceed a quarter of an inch in length. It, however, differs considerably in m y two specimens, being in both longer than the same in Audubon's specimen. In the urino-genital system of Plotus anhinga, in both sexes, the ducts open in the normal manner into the cloaca, just above its lower orifice. This orifice, however, is not on the surface, but is into a cavity, behind the cloaca, which opens externally quite close to the place where the two communicate. Except for this nearly marginal orifice the second cavity is a caecal sac, oval in shape, and about |
