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VIII. On the Structure and Development of the Skull of the Common Frog (Rana tem- 
poraria, L.). By William Kitchen Parker, F.R.S. 
Received October 10, 1870, — Read January 19, 1871. 
Introductory Remarks. 
Since the sending in of my last communication, that on the Skull of the Fowl, our 
knowledge of the morphology of the facial arches has been very greatly extended by 
Professor Huxley’s invaluable paper “On the Representatives of the Malleus and the Incus 
of the Mammalia in the other Vertebrata ” (see Proc. Zool. Soc. May 1869, pp. 391-407). 
After comparing the components of the mandibular and hyoid arches in an extended 
series of vertebrate types, the author concludes his paper by saying (p. 406), “ in the higher 
Amphibia changes of a most remarkable kind take place, of which I do not now propose 
to speak, as my friend Mr. Parker is engaged in working out that part of the subject.” 
The most important result of Professor FIuxley’s more recent researches into the 
subject is the rectification of a very obstructive error — namely, the supposition that the 
incus of the Mammal was the pier of the mandibular arch, thus making it the counter- 
part of the os quadratum of the Sauropsida. 
The type which has been most instructive in this matter is that remarkable New- 
Zealand Lizard ( Hatteria ) the structure of which has been so well worked out and 
described by Dr. Gunther (Phil. Trans. 1867, pp. 595-629), hi which the stapes is 
continuous with the hyoid arch. 
Taking this form as a practical stand-point, Professor Huxley has, after comparing 
its facial structures with those of the Crocodile and the Bird, proposed a nomenclature 
for the parts of the middle ear (largely formed by metamorphosis of the top of the 
hyoid arch), which should have the term “ stapes ” as a foundation. 
We thus get the terms “ suprastapedial,” “ infrastapedial,” and the like, all very useful 
terms in the description of these modified parts of the facial arches in the Sauropsida. 
Whilst my friend was working out this subject, it occurred to me to reexamine the 
condition of these parts in the tailless Amphibia ; I soon saw enough to allure me on 
to an extended observation of these structures, in the Frog ; and the longer I worked the 
more I saw the necessity for doing what Professor Huxley strongly advised me, namely, 
extending my observations backwards and downwards into the condition of these parts 
in very minute embryos. 
One thing soon appeared certain ; and that was the absolute morphological distinction, 
between the “ stapes ” or ear-plug , and the other bones or cartilages related to it phy- 
siologically as part of the middle ear. Nevertheless I see no reason for the non-adoption 
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