MORPHOLOGY OF THE VERTEBRATE SKULL 23 
MAMMALIAN AUDITORY OSSICLES 
In all the field of vertebrate morphology there is perhaps no 
more remarkable theory than that associated with the name of 
Reichert (’37). This theory deals with the origin of the auditory 
ossicles in stapediferous vertebrates; it holds that these ossicles 
represent the transformed elements of the visceral arches of 
fishes and in particular that the quadrate of reptiles is the homo- 
logue of the mammalian incus, the articular. of the malleus. 
Even before Reichert, Gaupp tells us (’11, p. 123) the homol- 
ogy of the malleus with the articular had been suggested by 
J. F. Meckel (’20) and the homology of the incus with the quad- 
rate by C. G. Carus (18). Like every other great theory, this 
one had to undergo a long period of opposition and during the 
preceding century it evoked an extensive literature. The whole 
subject was carefully reviewed independently by Gaupp (’99) and 
by Kingsley (00), and both of these authors strongly supported 
the Reichert theory. 
Since then Gaupp has further strengthened this doctrine in 
his work on the development of the skull of Echidna (’08) and 
in several later works (’05, ’09, 710, 711). Interest has been 
added to the subject by the polemical opposition of Fuchs (’09) to 
Gaupp. Many other workers, such as Bender, Driiner, Lubosch, 
Kjellberg, Schulman, Toldt, have also made valuable contribu- 
tions to the subject. 
In general the most important evidence for homologizing the 
quadrate and articular of reptiles with the incus and malleus 
respectively of mammals lies in the parallel, essentially identical, 
topographic relations and mode of development of these two sets 
of elements in the two classes. This parallelism in topographic 
relations and in development although marked by wide adaptive 
differences, is so fundamental, so extensive, so complex, that the 
possibility of these resemblances being accidental or due to 
convergent evolution seems practically excluded. 
To recall only a few points in this complex evidence® the mal- 
leus of mammals is developed as the proximal or articular portion 
5 For a fuller discussion, see Gregory, ‘‘The orders of mammals,’’ 1910, pp. 
125-143. 
