XIX.—On the Cranial Nerves ofChimæra monstrosa (Linn. 1754);with a Discussion of the Lateral Line System, and of the Morphology of theChorda tympani

Abstract

This investigation first commenced in the examination of a few special points which had arisen in connection with Professor Ewart's investigations on the Cranial Nerves and Lateral Sense Organs of Elasmobranchs. As this examination revealed facts of more interest than was expected, it occurred to me to investigate very thoroughly the whole of the cranial nerves of this animal, and to publish the results as a continuation of the work already alluded to. The research turned out to be much easier and more interesting than I had anticipated, and, as regards its cranial nerves at any rate, Chimæra is unrivalled among vertebrates, first, for the ease with which its nerves may be dissected, and second, for the almost ideal results that are to be obtained. The endless perplexity and mystification produced by the study of the trigeminal and facial nerves of the cartilaginous fishes,—dispelled to a very great extent, it is true, by the researches of Marshall and Spencer,—would probably have never arisen if Stannius had made a careful examination of the roots of the 5th and 7th nerves of his Chimæra. This, however, he omitted to do in the very form—in fact, as far as we know, the only form—which would have repaid the investigation ; and hence the embryologist stepped in and made a discovery that the anatomist had just, and only just, failed to grasp. The more important facts, therefore, relating to the cranial nerves of the Holocephali are, it is claimed, here recorded for the first time.