512 Dr. A. A. Gray. On the Anatomical [June 1, 
from that found in the rhea and in all the carinate birds hitherto examined, 
with the exception to be described in this paper, the penguin. The 
significance of this communication has already been discussed, from the 
evolutionary point of view,* but afew words may, with advantage, be added 
now. ‘The channel is present in many reptiles, but not in all, eg., the gecko 
and monitor. In birds it was supposed to ‘be invariably present until its 
absence was demonstrated by the writer in the ostrich and apteryx. In 
mammals, on the other hand, it has only been found to be present in a 
limited number of the polyprotodont marsupials and the insectivora. In such 
amphibia as have been examined, the frog and the toad, the channel was 
found to be present. 
It is thus difficult to account for the facts as they are manifest in birds. 
In their origin from veptiles, birds may either have possessed this channel 
and it has been lost in the ratite branch, with the exception of the rhea; or 
they may not have derived it from the reptilian stock, it having been acquired 
by the carinate birds and by the rhea among the ratite. On these two views, 
suggested by himself, the writer formerly declined to express an opinion as 
to which was the more probably correct. But, with the disposition of the 
canals in the emu, he is now rather inclined to the view that the channel of 
communication referred to has been acquired by the birds, and is not a 
remnant of reptilian ancestry. It is, of course, quite impossible to dogmatise, 
but in view of the fact that in the ostrich, emu, and apteryx, the channel 
is absent, and that that these are undoubtedly birds of an ancient type, the 
opinion above expressed seems the more probable, in spite of the fact that the 
rhea possesses the communication under discussion. Further, in support of 
this opinion, 1t should be pointed out that the communication is present in all 
carinate birds that have been examined by the writer, with the single 
exception of the penguin; and it is of considerable significance that the 
penguin is admittedly an archaic type of bird} The writer has in course of 
preparation the labyrinth of the cassowary, and its examination will throw 
fresh light upon this point. 
As regards the physiological significance of this channel of communication, 
if there is any such significance at all, it must be admitted that its function 
is obscure. The channel, when present, only allows of the passage of the 
perilymph from one canal to the other, the endolymph spaces of the two 
canals always remaining quite separate. 
The cochlea, ¢., of the emu is, in general, similar to those of the ratite birds. 
* Gray, op. cit., vol. 2, p. 95. 
+ Op. cit, vol. 251.92. 
t ‘Cambridge Nat. Hist.,’ vol. 9, p. 94. 
