IV.—A Monograph on the general Morphology of the Myxinoid Fishes, based on a study of Myxine. Part VI. The Morphology of the Vascular System

Abstract

The first five parts of this work on the skeleton, muscles, vascular system, and visceral organs were published in the Transactions of the Society in 1905, 1907, 1909, 1912, and 1913.The present section deals with a difficult and puzzling system which adds to its fundamental incongruity a range of variation which reduces the normal status to a condition of speculative uncertainty. The works of A. A. Retzius, J. Müller, and Jackson have resulted in a fairly accurate knowledge of the arterial system; but the venous system, which is much more important as regards its morphological bearings, is only imperfectly known, and the series of so-called veno-lymphatic spaces hardly known at all. Unhappily, material for a study of the development of the vascular system of Myxine has still to be obtained. The smallest individual out of many hundreds which I have collected was over 10 cm. long. Beard records a badly damaged 6·5 cm. specimen and Maas one of 8·5 cm. The structure of Beard's example, which I have examined, does not differ in any noteworthy respect from that of the adult, and hence throws no light on embryonic conditions. Consequently the interpretation of the venous system which has been adopted in this paper awaits embryological confirmation, and is to be regarded in the meantime as a working hypothesis only. The spawning grounds of Myxine have not yet been discovered, and it seems likely that the animal spawns in deep water in places remote from its summer resorts.