142 REPORT—1874, 
conclusicas do not accord with those enunciated by Mr. Parker in the very excel- 
lent and laborious memoir which I have cited. 
I find, in the first place, that there is no coalescence of the mandibular with the 
hyoidean arch, the latter merely becoming articulated with the former. 
Secondly, Mr. Parker’s “suprahyomandibular” is simply an outgrowth of the 
mandibular arch from that elbow or angle which it makes when the pedicle by 
which it is attached to the trabecula passes into the downward and forward inclined 
suspensorial portion of the arch. This outgrowth attaches itself to the periotic 
capsule, and, coalescing with it, becomes the otic process, or “superior crus of the 
suspensorium,” of the adult frog. a 
he hyoid arch, seen in the fourth stage, elongates, and its proximal end attaches 
itself to the periotic capsule in front of the fenestra ovalis, and close to the pedicle 
of the suspensorium, which position it retains throughout life. 
The columella auris arises as an outgrowth of a cartilaginous nodule, which 
appears at the anterior and superior part of the fenestra ovalis, in front of and 
above the stapes, but in immediate contact with it. It is to be found in frogs and 
toads which have just lost their tails, in which the gape does not extend further 
back than the posterior margin of the eye, and which have no tympanic cavity, as 
a short and slender rod, which projects but very slightly beyond the level of the 
stapes, its free end being continued into fibrous tissue, which runs towards the sus- 
pensorium, beneath the portio dura, and represents the suspensorio-stapedial liga- 
ment of the Urodela. ; 
This rod elongates, and its anterior or free end is carried outwards as the tym- 
pano-eustachian passage is developed. At the same time the free end becomes 
elongated at right angles to the direction of the rod, and gives rise to the “ extra- 
stapedial” portion, which is imbedded in the membrana tympani. Ossification 
takes place around the periphery of the middle of the rod; thus the medio-stapedial 
is produced. The inner portion becomes the rounded or pestle-shaped supra- 
stapedial, but retains its primitive place and connexions; whence we find it in the 
adult articulated in a fossa in that part of the periotic capsule which forms the 
front boundary of the fenestra ovalis, but in close contact with the stapes. 
The columella auris of the frog, therefore, is certainly not formed by the meta- 
morphosis of any part of either the mandibular or the hyoidean arches, such as 
they exist in the fourth stage of larval development. 
It may be said further that the columella undoubtedly appears to be developed 
from the side walls of the auditory capsule in the same way as the stapes; and 
some appearances have led me to suspect that it is originally in continuity with 
the stapes, but I am not quite sure that such is the case. 
Are we to conclude, therefore, that the columella is a product of the periotic 
capsule, such as the stapes has been assumed to be ? 
Here, I think, there is considerable ground for hesitation. It appears to me 
that the stapes is not so much “cut out” of the cartilaginous periotic capsule as 
the result of the chondrification of a portion of that capsule which remains un- 
chondrified longer than the rest. 
Moreover the Urodela all possess a band of ligamentous fibres which extends 
from the stapes to that part of the suspensorium with which the hyoid is connected 
and to the hyoid itself. It is conceivable, and certainly not improbable, that this 
stapedio-suspensorial ligament represents the dorsal extremity of the hyoidean 
arch. But the columella auris in its early condition in the frog so nearly resembles 
the ete aa ligament partially chondrified, that it is hard to suppose 
that one is not the homologue of the other; in which case the columella, and even 
the stapes itself, may, after all, represent the metamorphosed dorsal end of the 
hyoidean arch or the hyomandibular of a fish. And it must be admitted that the 
relation of the portio dura nerve to the hyomandibular of a ray speaks strongly in 
favour of this view. 
On the Development of the Eye of the Cephalopoda. 
By EK. Ray Layxester, M.A. 
