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Show 534 MR. A. E. SHIPLEY ON SOME [June 19, very regularly towards the external end of the cells, and the body of the cell is crowded with granules, in some cases a thin layer of black granules lies just within the internal ends of the cells (fig. 3). There is no differentiation into parts of this long tube of columnar cells, but the tube is a compressed one, its long axis lying between the two lateral lines ; at the sides, as is shown in fig. 1, the lining cells are much flatter, and instead of being columnar become cubical. As seems to m e not unfrequent in parasitic Nematodes, the intestine contains no trace of food, only the above-mentioned vesicles, and these sometimes in great numbers. The body-cavity, which, as Hamann * has pointed out, cannot be regarded as homologous with the ccelom of, for instance, a Lumbricus, contains a fluid in which numerous small deeply staining granules, probably cells, float. It had coagulated in the anterior end of the body of m y specimens in irregular strands and fibrils, which formed a loose network running between the inner ends of the muscles and the outside of the intestine, as shown in fig. 2. At first I was almost inclined to regard this as evidence of the existence of a splanchnic layer of mesoblast, but its true nature soon became apparent. The proctodasum is very short and lined by a cuticle, continuous on one side with that of the intestine and on the other with the external cuticle. The line of demarcation is very sharply marked (fig. 4). The columnar epithelium ceases suddenly, and just behind this is a recess or groove, partly formed by the increase at this spot of the thickness of the wall of the tube by a muscle which probably acts as a sphincter. In this region of the body the distribution of the nerves has been admirably described by Hesse for Ascaris megalocephala, and although the preservation of m y material did not permit me to follow out all finer details of this system, I have no reason to doubt the correctness of his observations. Immediately behind, or at about the same level as the sphincter muscle, lie three problematical bodies, which are very conspicuous in both longitudinal and transverse sections, yet which have as a rule escaped the notice of workers at this group. Hesse mentions these structures and calls them " Gewebepolstern," which does not help us much ; he suggests they may have an excretory function. It is of course not impossible that these bodies may serve as a place where the waste nitrogeuous material is stored up within the body of the animal, such as is found in some Ascidians: but there is no evidence of this, and the canals in the lateral line, which are usually regarded as excretory, have a quite adequate opening to the exterior. At first sight these " Gewebepolstern " might easily be taken for three gigantic cells encircling the rectum close behind the level where the columnar cells of the intestine cease and the rectum 1 " Zur Entstehung des Exkretionsorganes der Seitenlinien und der Leibes-hohle der Nematoden," Centralbl. fur Bakteriologie, B d xi. 1892. |