1908.) Structure and Relationships of the Labyrinth. 521 
result of the long sojourn of the head in alcohol before it was given to the 
writer for preparation of the labyrinths; and the deposits seen in the cochlea 
and vestibule may possibly be explained in the same way. 
In comparing the labyrinth of the echidna with that of the platypus, it 
must first be noticed that there are greater differences than has hitherto been 
supposed. The considerable increase in the curvature of the cochlea of the 
echidna, as compared with that of the platypus, has already been mentioned, 
and need not be referred to further. But in the canals also the disposition 
of the structures is very different in the two animals. As was shown above, 
the canals of the echidna are curved in outline and completely mammalhan 
in type. Inthe platypus, on the other hand, the superior canal is noticeably 
angular and it meets the posterior canal abruptly, both of which features are 
characteristic of the reptilian labyrinth. The specimen of the labyrinth 
of the platypus obtained by the writer was a poor one, owing to the presence 
of heemorrhagic opacities, and it cannot be determined whether that labyrinth 
possesses a recessus utriculi or not. The aqueduct of the cochlea also was 
removed in the labyrinth of the platypus, so in this feature also, com- 
parison cannot be made between the labyrinths of the two animals. But in 
every other feature, at any rate so far as macroscopic evidence goes, the 
labyrinth of the echidna, though possessmg many distinctive reptilian 
features, is clearly a more definite advance towards the mammalian type than 
is that of the platypus. 
The Relationships of the Aqueduct of the Perilymph, the Perilumph Recess, and 
the Round Window to one another, and to the Cochlea. 
In the labyrinths of the animals just described, certain facts are elicited 
which throw considerable light upon the difficult question of the relationship 
of the structures mentioned above. It is still a matter of doubt, in spite of 
the careful investigations of Hasse, Retzius, Harrison, Gaupp, Versluys and 
others, as to what particular structure, for example, in birds and reptiles 
corresponds to the round window of the mammals. The difficulty has, of 
course, arisen from the fact that investigations have hitherto been made by 
means of the examination of numerous serial microscopic sections or by 
casts of the organ, and it is not surprising, therefore, that differences of 
opinion exist in regard to the relationships of the different structures. By 
the method employed in making the preparations from which the descriptions 
in these pages are taken, some at least of the causes of error are eliminated. 
In general it may be said, in respect to the relationships of the aqueduct 
of the perilymph, the perilymph recess, the round window and the cochlea, 
that in the reptile the condition is the most complicated, in the bird rather 
