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Show 1 9 0 4 .] ANATOMY OP PELAGIC SERPENTS. 149 division of the liver by furrows running at right angles to the longitudinal axis ot the body-is more marked. 1 counted five of these transverse furrows, which vary in depth and divide the liver into a series of segments of hepatic substance. As I shall point out later (see p. 151), Ilydrus platyurus shows the same segmentation of the liver. Milne-Edwards observes* of the liver of Typhlops that it is " divise en lobes plats," and this lobation is figured also by Cope t ; but it does not appear to be by any means so regular as in Platyurus. One cannot but put down this marked lobation to the regular bending of the body in swimming, and it forms an example of " segmentation " probably traceable to a definite mechanical cause. The gall-bladder gives oft'a single duct which soon forms a very complicated network in connection with the hepatic duct. This network is very much more complex than in Ilydrus, and the rete of ducts is so long before it enters the duodenum that the gallbladder can be dissected out and pulled much further away from the alimentary canal than is possible in Ilydrus. The pancreas seems to me to be smaller proportionately (it certainly is so actually) than in Ilydrus. The coiled region of the intestine is very long. When the coils are left undisturbed within their ccelomic space, they measure | of an inch, but when unwrapped no less than 5 inches. The kidneys are approximately equal in size, each measuring about 4 inch in length. They are broad in proportion to their length, and almost suggest those of the Boid Eryx. The right, anterior, kidney hardly at all overlaps the left, which commences where it ends. § Lung. It has been pointed out by several zoologists, including Cope j, that Platyurus and some other genera of Sea-Serpents possess the tracheal lung found also in a few genera of terrestrial Colubrines. Cope's statement on the matter is as follows:-" Finally the tracheal lung, as I shall call it, is distinct from the true lung in Platyurus and in Chersydrus. In the former of these genera, the trachea is not separate from the lumen." I do not think, however, that any detailed description of the lung exists. I shall endeavour therefore to supply this omission by the following description. There is no trace that I could discover of a second lung. The single lung extends to within one inch of the cloacal aperture and ends abruptly without any special diminution of calibre. It lies, posteriorly at any rate, on the right-hand side and is firmly bound to the dorsal parietes. The tracheal lung is, as Cope says, distinct from the bronchial lung; the two are separated at the end of the one and the beginning of the other by one of the pulmonary vessels which passes between them. The tracheal lung begins very high up in the body, close behind the head ; it ends posteriorly just in front of the origin from the heart of the right aortic arch. * ‘ Lemons sur la Physiologie et l'Anatomie comparee.' t " On the Lungs of the Ophidia," Proc. Amer. Phil. Soc. xxxiii. 1894. J Lor. cit. p. ‘217. |