Miscellaneous. 389 
‘even in the Marsupialia. The absence of the articulation with the 
lower jaw seemed to me to be of the less importance, as the qua- 
drate bone is also inconstant in its other unions, and only that with 
the squamous portion of the temporal is constant. That a distinct 
bone, which is constant throughout the whole series of the Mam- 
‘malia, should at once disappear, seemed to me to be improbable; 
nor could I accept the small fragments of bone found in birds, by 
‘some observers, as representing it. 
I could never reconcile myself to the opinion, supported especially 
by Reichert and Huxley, that the incus of the Mammalia is the 
homologue of the quadrate bone, both on account of the objections 
raised against it by J. Miiller*, who had the opportunity of care- 
fully examining the preparations made by M. Reichert for the 
proof of his opinion, and also because it seemed to me very impro- 
bable that the incus, which in the Ornithorhynchus does not occur at 
all, or only appears as a minute rudiment, should suddenly make 
its appearance again in the Birds in such gigantic proportions and 
in a totally different position, not to mention the difficulty of inter- 
preting the incus and malleus which certainly likewise occur in a 
cartilaginous rudimentary state in Birdst. 
Leaving this last circumstance, especially, out of consideration, 
from the similarity which two parts issuing from or connected with 
Meckel’s process (namely, the articular portion of the lower jaw in 
Birds and Amphibia, and the malleus of the Mammalia lying behind 
the lower jaw) present to one another at a certain period of deve- 
lopment, a conclusion is arrived at as to the homology of these 
parts, upon which a number of other hypotheses upon the homologies 
of other parts of the skeleton (e.g. in the fishes) are supported ; and 
the latter, of course, fall if the former be erroneous. 
At the present moment, when I am occupied with the conclusion 
of other investigations, I should hardly have been led to take up © 
again a question which has been so long in dispute, if Mr. Huxley, 
who had already + given his decided adhesion to the opinion of the 
homology of the quadrate bone and the incus, had not, in a memoir 
upon the classification of Birds, otherwise containing much that is 
admirable, and which is destined to find a very large circle of 
readers, represented the matter as if all doubt upon the point in 
question had been got rid of §. 
As it appeared to me that a solution of the question was most 
likely to be found among the lower Mammalia, which approach 
_ Birds in so many respects, I first sought for it among the Monotre- 
mata, but have been compelled to interrupt this investigation for 
the present, and in the next place took young Marsupials in hand, 
* Archiv fiir Anatomie und Physiologie, 1838, p. clxxxvii. 
+ Even if there may be some doubt with iuiad to the incus in Birds, 
this must be quite baseless with respect to the malleus. But the bone 
which is denominated incus in the Mammalia is always situated between 
the stapes and the malleus. 
¢ Lectures on the Elements of Comparative Anatomy. London, 1864, 
pp. 229 et seg. 
~ § Proc. Zool. Soc, London, 1867, p. 416. 
