399 



in der ganzen Reihe der Amnioten bewiesen. Ich muß aber zugeben, 

 daß dieser Punkt noch nicht feststeht." 



This would undoubtedly be a proof that, as I assume, the extra- 

 columella is equivalent with the incus and malleus, but it is not a 

 conditio sine qua non. It would be very ambitious to try and 

 homologize piece for piece and joint for joint of the auditory chain of 

 the Sauropsida with that of the Mammalia. The great variety in the 

 number of jointed pieces in the various Anura (some of them with 

 four pieces as in the Mammalia) makes it for instance very hazardous 

 to fix upon the homology of the Sauropsidan stapes - extracolumellar 

 joint. In the Mammalia we have the lentiforme situated just at the 

 critical place and of somewhat doubtful provenience. We cannot even 

 homologize with certainty the various extracolumellar processes (e. g. 

 extra, supra, infrastapedial, additional etc. processes) of the various 

 Reptilia. Lastly, the vagaries of the proximal end of the hyoid are 

 so great, both ontogenetic and in the adult condition, that our know- 

 ledge is in this respect in a state of great confusion. With the few 

 forms hitherto studied we are as yet unable to weed out the ceno- 

 genetic features. Take for instance the everlasting question about the 

 hyoidean connexions of Sphenodon. Howes ^) in his splendid paper 

 has found that the extra- and suprastapedial processes are continuous 

 with each other, are both parts of the extracolumella , and that the 

 extrastapedial is continuous with the hyoid horn — in the procarti- 

 laginous stage. This is exactly what ontogeny might be expected to 

 show, provided the hyoid has phyletically passed long enough over the 

 lateral end of the extracolumellar plate. In any case his drawing 

 agrees remarkably with one by Kingsley of an embryonic Lizard, 

 where however the top end of the hyoid joins the stapes, medially 

 from the extra-columella , exactly conforming with the desideratum 

 mentioned by Versluys. Something very similar happens in Birds 

 cf. for instance Bronn's Vögel, Taf. 46, and Suschkin's admirable 

 monograph on the skull of Tin nun cuius ^), Figs. 19, 86 etc., and it is 

 very interesting that the same careful observer has found no trace 

 of a connexion between the mandible and the second arch, an un- 

 deniable fact from which however nobody has any business to conclude 

 that such a connection does not exist in other birds, for instance in 



1) On the Development of the Skeleton of the Tuatara, Sphe- 

 nodon punctatus. Trans. Zool. Soc, Vol. 16, Pt. 1, Febr. 1901. 



2) Zur Morphologie des Vogelskelets. Nouveaux Memoires Soc. 

 Imp. Moscou, T. 16, 1899, 2. 



