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Show 150 DR . E. L O N N B E R G O N T H E [Feb. 20, are not nearly so high as in Bos \ and hardly so high as in Ovis and Capra. They measure 2-3 m m . in height, but this may partly be due to contraction. The free margins of these walls in the fundus are finely denticulated, but all of them are provided with vertical ridges on their lateral surfaces. The cells are again partly divided by smaller walls into secondary cells, but this is quite irregular. The cellular interspaces are also finely reticulated by small tertiary ridges which carry small conical papilla?, and such are also found within the tertiary reticulations. This is conspicuous on places where the epithelial covering has fallen off. The reticulum of Ovibos is thus much more differentiated than that of Rangifer and Capreolus, in which the cells are very shallow. The difference between Ovibos and Rangifer, which both lead a similar life, indicates that no parallelism in development has taken place with regard to this organ. This, on the other hand, seems to prove that the suggestion made by Owen2 , that the shallowness of the cells of the Reindeer's reticulum is due to the fact that the animal obtains so much water by its swallowing snow that any reservoir for water is unnecessary, is incorrect. Ovibos is a representative of a more specialized ruminant type. The diameters of the reticulum of Ovibos are 160 x 210 mm., and those of the psalterium 180 x 230. The latter is thus larger ; and therein Ovibos agrees with Bos, and differs from Ovis, Capra, and the Cervidce3. The number of folds in the psalterium is 61, and their arrangement is plainly quadruplicate, with folds, or septa, of first, second, third, and fourth order. Eight folds of the first order are conspicuous, embracing 7 pockets of the first order. There ought, then, to be 57 folds, if it were quite regular, but some few of the fourth order are not developed ; on the other hand, there are some outside the seven pockets belonging to incomplete pockets. The quadruplicate arrangement agrees with that in Ovis, the same in Bos being quinquiplicate. I do not think, however, that much stress can be laid upon this character ; this opinion being confirmed by the fact that Garrod has found in the genus Cervus forms with quinqui-, quadri-, and triplicate arrangement of these septa *. Capreolus is said to have a quadriplicate arrangement of septa in the psalterium; but before m e lies a specimen which has only a triplicate arrangement, without the slightest trace of the fourth system of folds. Likewise I have a psalterium of Capra with only a few indications of the folds of the fourth system 5. The psalterium-folds are beset with conical papillae, usually almost as broad as high (about 1| mm.), but more acute towards the free margin of the folds than at their bases. At the opening 1 Vergl. Anat. d. Hausthiere, achte Auflage, 1896. 2 Anat. of Vertebrates, vol. iii. p. 472. 3 At least Capreolus, Cervus dama, and C. elaphus. 4 Proc. Zool. Soc. 1877, pp. 2 et seqq. 5 Boas has also pointed out the variability of this organ (Morph. Jahrb. 1890). |