370 On the Morphology of the Semicircular Canals, (June, 
media of mammals; but with this we have at present nothing 
to do. 
Evidently the first stage of the development of the ear, the 
process of inflexion, belongs to the indirect method, but the fact 
that this process is still so pronounced, and the fact that the otic 
vesicle when once shut off from the epiblast rapidly enlarges, so 
that the area of the enclosed surface is relatively very great, would 
indicate to my mind that in our remote ancestors, this process of 
inflexion was very marked—that it was extensive, involving a 
a comparatively large area, and bringing about great modifica- 
tions of structure. The tendency in the constant repetition of 
this process would be to diminish its relative importance, 2. e., to 
make it constantly less and less pronounced, Probably, see 
fore, the amount of surface actually inflected in the embryo is 
small compared with the area inflected in the process of ancestral 
development. To this we will presently return. 
The special parts of the labyrinth appear to be formed by a 
direct method. ‘This would, of course, as we have seen reason 
to believe, not exclude the possibility of an indirect method 
having obtained in our remote progenitors. 
Having now compared the various methods pursued in the 
development of the mucous canals and the ear, let us recall a 
fact which has not yet been brought into sufficient prominence, 
namely, that the structure of the mucous canals and that of the 
semicircular canals is very similar. In 1850 Leydig! already 
noticed this fact, for he compares a semicircular canal and its 
ampulla with a mucous canal and its “ nervebutton.” Both struc- 
tures consist of connective tissue lined with epithelium, and the 
“nervebutton ” of one corresponds to the macula acustica of the 
other. The analogy seems complete. 
Would it now be too hazardous to suggest that two organs 
which are so closely related in structure, which present such sig- 
nificant facts, as regards nerve supply and embryological develop- 
ment, are related genetically? Such a supposition would evi- 
dently not be inconsistent. Let us see how it may have been 
brought about. In an organism provided with a general apparatus 
for the perception of vibrations, evidently the first thing that 
would take place would be a specialization of certain portions for 
certain classes of vibrations. This is what may have been the 
case with the lateral canals and the ear, each being a specialigi 
i Mustier’s Archiv.—Schleimkan. d. Knochenfische. - 
