a) Dr. A. A. Gray. On the Anatomical [June 1, 
the vestibule is 2°5 mm. and the diameter of the canal itself at the vertex is 
0-75 mm. 
The cochlea is only possessed of half a turn and the straight distance 
from the anterior margin of the round window to the tip of the cochlea 
is 45 mm. 
As stated above, there are numerous points of interest connected with the 
labyrinth of the echidna, some of which have been known previously, while 
others are now recorded. Further, certain errors, which inevitably arise 
from the attempt to reconstruct a whole larger structure from numerous 
fine microscopic seetions, may be corrected when the organ is viewed as a 
whole. 
_ Considered as a whole, the labyrinth of the echidna, while approaching 
rather more nearly the mammalian than the reptilian type, presents several 
remarkable similarities to the latter. Thus, as has been shown by previous 
anatomists, there is a lagena, /., at the tip of the cochlea, and this structure 
is seen in fig. 10 as an oval cavity in that portion of the tip of the organ 
which lies nearest to the vestibule. It is supplied by a nerve, but it is not 
possible to say whether otoliths are present in the lagena or not. The 
specimen lay in rectified spirit for very many years, and it is quite possible 
that during that time they were dissolved if ever present. Since the 
processes for ordinary microscopic examination permit the contact of acids, 
otoliths, when present, are at once dissolved, so that the work of previous 
anatomists does not elucidate the matter. The question could be decided by 
preparing a comparatively fresh specimen by the writer’s method, by which 
means otoliths are preserved, as is shown in the case of the reptile and 
the bird. 
It has been shown by previous anatomists that the cochlea of the echidna 
only possesses a portion of a turn, but, judging from the figures drawn to 
represent the organ, a somewhat erroneous impression has been conveyed. 
As a matter of fact, the cochlea, ¢., of the echidna presents the appearance of 
a larger portion of a circle than is usually depicted, most representations 
making it appear very similar to that of the platypus. In reality, the 
labyrinth of the echidna presents in this, as in other respects, a very 
considerable advance upon that of the platypus, in which there is only the 
slightest degree of curvature in the cochlea, with a bulbous knob on the tip of 
the organ.* 
The aqueduct of the cochlea in echidna is a structure whose relationships 
are clearly reminiscent of its reptilian ancestry. Out of the base of the 
cochlea there opens, by a large oval aperture, an egg-shaped cavity, which 
* Gray, op. cit., vol. 2, p. 81. 
