REPORT ON THE SPHENISCID^. 205 



another the septum did not extend more than |^th of an inch in front of the bifurca- 

 tion. The tracheal septum varies in length in different species, but it appears to bear 

 no relation whatever to sex. This is shown in the subjoined table. With reo-ard to 

 structure, the septum tracheae resembles that of the tracheal walls in the possession of 

 cartilaginous bars which are continuous with the rings of the trachea. These bars are 

 included within a double fold of the tracheal mucous membrane, which, together with the 

 cartilaginous elements, completes the septum. The posterior extremity of the septum 

 tracheae is attached to the point of bifurcation of the two bronchial tubes, while its 

 anterior extremity invariably presents a hollowed, concave, sharp margin in front of which 

 the tracheal tube is single and undivided. The appearance of cartilaginous bars in the 

 septum seems to show that in the Penguins this septum tracheae presents a persistent 

 condition of that stage of development of the early embryo of the chick, in which the two 

 diverticula which ultimately form the lungs and bronchial tubes open separately into the 

 oesophagus. In the chick, these diverticula having developed to form the lungs, com- 

 municate with the oesophagus by means of a tube (the trachea) which is single through- 

 out, whereas in the Penguins it would appear that the septum, which originally separates 

 the two diverticula persists throughout life to a greater or less extent in different species. 

 In Evdyptes chrysocome from Tristan, the last four tracheal rings are welded together to 

 form a single immoveable mass, to which the bronchial tubes are attached. 



The Syrinx. 



The framework of the lower larynx of Eudyptes chrysocome from Tristan d'Acunha 

 consists of the last four tracheal rings. Of these the last three, being situated behind 

 the point of bifurcation, in reahty belong rather to the bronchial tubes than to the 

 trachea. In as much as they are inseparably united with the last tracheal ring, how- 

 ever, it is more convenient to enumerate them as structurally connected with the larger 

 tube. The last tracheal ring proper is provided with a mesial process, or pessulus, 

 which lies in the bronchial fork and adapts the posterior extremity of the trachea to the 

 commencement of the bronchial tubes. To this the following three rings on either 

 side are immoveal^ly united to form a single osseous mass. Between the last of these rings 

 and the first bronchial bar proper there exists on the ventral surface of the bronchus an 

 elliptical space, which is filled by an elastic membrane. The dorsal surface of the 

 syrinx on either side of the middle line is completed l^y means of a broad, elastic 

 membrane, which extends along the whole length of the corresponding bronchial tube, 

 and forms the dorsal wall of the latter. This is apparently the essential part of the 

 organ of voice, as apart from it and the elliptical membrane on the ventral surface 

 of the bronchus the larynx possesses no vibrating structure. The lower larynx is entirely 

 devoid of intrinsic muscles, and only in certain species does the contractor tracheae extend 



