1901.] LARYirX OF CBETAIIS' WHALES. 295 



is rauch pitted ; the pits lead into long tubular branching tubes, 

 terminating blindly ; they liave not a muscular wall, nor is there 

 any glandular tissue here (as in Risso'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 coutiuued to the commencement of the 

 trachea, but naturally they become shorter ns 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 BnlcenojJtera, as well as in Cogia and other Odontocetes 

 (c/. Murie's fig. of a longitudinal section of the larynx in Eisso'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 

 prepai'ation, 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. Geiteral Eemarks, 



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 Mnrie (1871, p. 130) considers the " parallel folds " at the base 

 of the epiglottis in Eisso'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 Man 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* 



