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Show 230 ON THE OBLIQUE SEPTA IN THE PASSERINES. [Feb. 4, of that reptile are invested by a closely adherent membrane, which has been thus described by Prof. Huxley l:-" A fibrous expansion extends from the vertebral column over the anterior face of the stomach, the liver, and the dorsal and front aspect of the pericardium, to the sternum and the parietes of the thorax, separating the thoraco-abdominal space into a respiratory and a cardio-abdominal cavity, and representing the oblique septum of the bird." Both 1 2 and Mr. G. W . Butler3 have included in the comparison which Prof. Huxley thus made the omentum of the bird. But this does not interfere with the special likeness which the Passerine shows to the Crocodile, in that the representative of the oblique septum of other birds has not (as a rule) a ventral attachment on each side to the sternum, but that it forms a closely investing sheath to the liver-lobes ; but it is very doubtful whether this resemblance is more than a superficial one. It is agreed on all hands that the Passeres are a much, if not the most, specialized group of birds, standing on the very topmost branch of the avian tree. Among them, therefore, the retention of archaic characters, though possible, would not be so likely as among some other groups. Besides, the arrangement of the oblique septa in them seems to be a secondary affair on account of the fact that the original (?) position of the attachment of those septa is indicated by rudiments varying in degree of the portion of the septa which was formerly inserted laterally and ventrally on to the sternum, and the Rook has these membranes complete. This may be in the form of a much-fenestrated membrane, or there may be but a single tag on each side near to the posterior margin of the sternum, or, as in an example of Prosihemadera novae-zealandice, the attachment may have been completely retained on one side. I should be disposed, therefore, in spite of certain undeniable likenesses which the Passerines show to the Crocodilia, to regard the relations of the oblique septa in them as a modification of the more prevalent disposition of those parts. In describing the septa of the somewhat aberrant Australian Struthidea, I called attention to the fact that the liver-lobes were partly shut off from the subomental space by membranous partitions. The exact way in which these partitions are related to the liver-lobes is, so far as m y experience goes, unique among birds. But there are other birds in which an arrangement of the same kind exists; but with certain differences. In several birds, for instance in Chrysotis guildingi, the left liver-lobe is completely shut off from the subomental space by a vertical transverse partition ; there is no corresponding partition on the opposite side of the body. There are some birds in which, as in Struthidea, there are partitions on both sides ; but in them the partitions fr1*2o mL" o Oct.nh ectt hihse te u.aS R bruepbeos.d mp iq5ievu6rniia8sttt.iaoe orl nyc o oOfsr mptgphaealc neeBso,t d einyn o- cactean rvmdtia etierynn e itDnlii yLrvi eizplnaaygrr dBtsisihra &udlcts.l,, y""o f aPf.s. Zti..h nSSe. . S l1ti8vr8e89ur,t- hlppo..i b d42e55es36a. . . |
