418 DR MORRISON WATSON AND MR ALFRED H. YOUNG 
an exterior covering of a strong layer of muscles.” That the presence of a 
ventral uir-sac in connection with the larynx of whalebone whales is of constant 
occurrence may be correct; certainly in them it attains its greatest development. 
But it is by no means so clear that it can be regarded as a specific character of 
the whalebone group. On the contrary, the existence of a small but analogous 
sac which, as Dr Murie* points out, ‘fills in great part the angle of junction 
between the enlarged epiglottis and the thyroid cartilage, but does not reach the 
posterior border of the latter,” in Risso’s Grampus, shows that the arrangement 
in question is not confined to the whalebone whales. In Beluga, as we have 
seen, the arrangement is similar to that described in Risso’s Grampus, and Dr 
Mourte’st assertion that the above apparent distinction between the whalebone 
and toothed whales is one rather of degree than of kind, is thereby corroborated. 
The truth of this observation is rendered still more apparent by a comparison of 
Dr Murie’s figure of the sac in Risso’s Grampus with that of the same structure 
in the Balenoptera Sibbaldii described by Professor TURNER. f 
Be this as it may, the great difference in the shape and connections of the 
laryngeal cartilages in whalebone whales, as contrasted with those of the toothed 
species, is sufficient to differentiate the two groups. 
Cuvier § affirms the absence both of ventricles and of vocal cords in the 
cetacean larynx, and, so far as the latter are concerned, we agree with his 
observations, notwithstanding Dr Murik’s|| assertion that rudimentary vocal 
cords are present in the larynx of Grampus. At least in Beluga, with the ex- 
ception of the free margins of the arytenoid cartilages, we could not distinguish 
any structure which could functionally represent these cords. With regard to 
the laryngeal ventricles, on the other hand, we must differ from the distinguished 
French anatomist. We have already directed attention to the presence in the 
larynx of Beluga of two pouches which correspond in position to the ventricles 
of other mammals, and that they ought really to be regarded as homologous 
with such seems proved by the following considerations :—Firstly, That their 
relation to the thyroid cartilage aud to the thyro-arytenoid muscles is the same 
in both ; secondly, That in some ruminants, ¢g., Saiga tartarica, as pointed 
out by Dr Murtg, the arrangement of the ventricles is similar to that described 
above in Beluga, these ventricles forming a single pouch which projects down- 
ward and backward into the hollow of the thyroid cartilage. In the ruminants 
referred to, moreover, as in those whales which possess a laryngeal sac, there 
is no trace of any other cavity which can correspond to the laryngeal ventricles, 
Thirdly, That this sac in Beluga is essentially a bilateral structure is shown 
by the presence of the anterior mesial fold in its interior, which, were it de- 
{ XVII. plate viii. fig. 36. 
* X. p. 127. + X. p. 197 
| X 0, q XXXIX. p. 491. 
§ XXXI. vol. iv. p. 54. | 
