8 ON THE CETACEAN LARYNX. 
Fig. 14. Larynx oF BALAENOPTERA MUSCULUS (x 3). (After BeavREGARD and BouaRt.) 
One of the great aryteno-epiglottidean folds is opened to show the horn of the arytenoid lying within. 
In regard to other morphological points, the Cetacean larynx, so far as the 
above description goes, supports Dusois’s* view that the cricoids and arytenoids 
come from a different morphological origin to that of the thyroid; and that while 
the latter is derived from the visceral arches, they are modifications of the anterior 
rings of the trachea. If that be the case, our Cetacean larynges would suggest that 
the cricoid, the arytenoids, and the supra-arytenoids are formed out of three such 
tracheal rings. The shape of the arytenoids in the Balaenoidea and of the supra- 
arytenoids in the Delphinoidea appear to me to favour this view somewhat. But 
these larynges do not help us in regard to the thyroid cartilage, in settling, for 
instance, whether it arises from two visceral arches, as it appears evidently to do in 
the Monotremata. The origin of the epiglottis is a difficulty, and its form and 
structure in the Cetacea are not the least remarkable features in the group. 
Taking it as proven that the thyroid cartilage originates from the visceral skeleton 
in some such way as Dusots asserts, and considering the relations of the epiglottis 
to the thyroid in Cetacea, and in their young stages to the basi-hyal also, I am 
inclined to suspect that the cartilaginous epiglottis in Cetacea is a somewhat 
ancient type, and was really developed from the copula or basi-branchial skeleton 
uniting the thyroid and hyoid arches. But earlier stages than I possess would be 
required to support this inference. 
* Hua. Dusors. Zur Morphologie des Larynx. Anat. Anz, I., pp. 178, 225. 1886. 
