1908.] Structure and Relationships of the Labyrinth. 5f5 
the vestibule is rather less than 3°5 mm., and the diameter of the canal 
itself at its vertex is rather less than 15 mm. The horizontal canal has 
internal and external diameters of 5 and 7 mm. respectively. The height 
of the vertex of the canal above the vestibule is rather more than 35 mm., 
and the diameter of the canal itself at its vertex is 15 mm. 
In the ‘specimen of the labyrinth of the penguin which is represented 
in fig. 7, ete., air-bubbles unfortunately made their appearance in the 
celloidin in which the structures are embedded, and this interferes to a 
certain extent with the view of the parts. In addition to this the perilymph 
recess has been in part broken off. 
In its general appearance the labyrinth of the penguin approaches most 
nearly to that of the red-throated diver among all the birds which have so 
far been examined. This is particularly noticeable in the cochlea, which 
terminates not as a rounded or bulbous extremity as in other birds, but 
comes rather to a tapering point. In both birds the superior canal, s., is of 
the “drooping” type, and has the form of a long ellipse. 
In the canals of the penguin, as in almost all birds, the perilymph space 
is well marked. The cristae acustice in the ampulle are “simple,” there 
being only one crest in that portion of the neuro-epithelium which lies on 
the floor of the ampulle. There is one peculiarity about the canals of the 
penguin which should be noted. There appears to be no channel of 
communication between the perilymph spaces of the horizontal and posterior 
canals at the point at which they cross, x On close examination there 
does seem to be contact between the walls of the canals, but no actual 
channel from one to the other can be found in the specimen from which 
this description is taken. In this respect, therefore, the labyrinth of the 
penguin is somewhat similar to those of the ostrich, the emu, and the 
apteryx, and differs from all other birds which have been examined 
hitherto. 
The cochlea, ¢., of the penguin is of a rather primitive type in comparison 
with those of other carinate birds. The organ is proportionately somewhat 
short, the basilar portion being particularly small in extent. 
The cartilaginous structures, c.f, in the cochlea of the penguin deserve 
notice. It has been stated by some anatomists, that in the avian cochlea 
there are two cartilaginous plates which unite at their distal extremities in 
the region of the lagena, while each plate has its own termination at the 
vestibular end of the cochlea. This statement may be, and probably is, true 
in respect to some birds, but, as was pointed out by the writer, it is not true 
of all,* eg. the rhea. In this bird, the cartilaginous structure consists of 
| * Op. cit., vol. 2, p. 122. 
