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Show 1901.] LARYNX OP CERTAIN WHALES. 295 is much pitted ; the pits lead into long tubular branching tubes, terminating blindly ; they have not a muscular wall, nor is there any glandular tissue here (as in Bisso's Grampus). These tubes are not seen well in the section, which involves the median septum, but the ends and sides of the tubes of the right (i. e. removed) pouch are seen adhering to this septum, and thus excluding the possibility of the existence of a median pouch. The series of pits is continued to the commencement of the trachea, but naturally they become shorter as this is approached. These tubes lie between the cavity of the larynx and the thyroid cartilage, filling up the angle between the latter and the epiglottis, mingled with connective tissue and some blood-vessels. They are evidently of the same nature as the pits visible on a less extensive scale in Balcenoptera, as well as in Cogia and other Odontocetes (cf. Murie's fig. of a longitudinal section of the larynx in Bisso's Grampus (1871), p. 128). The lining of the back and sides of the larynx, and of so much of the trachea as is present in the preparation, is thrown into a series of parallel, equidistant, and well-defined ridges, which start-each by two or three " roots " - at the hinder margin of the arytenoid; these are not mere foldings of the mucous membrane due to shrinkage, but are extremely well-defined. IV. GENERAL BEMARKS. Two points of general interest are presented by the larynx of the Cetacea : firstly, the absence of vocal cords, and even of any rudiment of them; secondly, the peculiar modifications undergone by the arytenoid cartilage. As to the former, little more than the statement is necessary ; possibly the disappearance (? primitive absence) of all rudiments is related to the second point. It may be noted, however, that some authors have attempted to identify certain structures as being the rudiments of the cords; thus Murie (1371, p. 130) considers the " parallel folds " at the base of the epiglottis in Bisso's Grampus, which form the margins of the entrance to a small sublaryngeal sac, as their representatives. These, however, pass from epiglottis to thyroid, instead of from arytenoid to thyroid, and more recent authorities, e.g. Dubois, deny the existence of vocal cords in the Cetacea. As to the modifications of the " arytenoid cartilage," not only do we find it under two very different forms in the Mystacocetes on the one hand, and the Odontocetes on the other, but both these agree in the fact that this cartilage represents something more than the true arytenoid in M a n and Dog. Howes (1879) pointed out that in the young Porpoise there are two cartilages closely united by connective-tissue, but distinctly separate; not only in the young, but in the adult, are these cartilages distinct. He gave reasons for believing that the upper of these cartilages-the supra-arytenoid, as D'Arcy Thompson named it later-represents, in all probability, the cartilage of Wrisberg of the Dog's larynx ; in this view he was confirmed by Cleland (1884), who finds a similar condition in the Dolphin. At a later date, D'Arcy Thompson (1890), as the outcome of an 20* |