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points in its favour: 1) The chain between the fenestra ovalis and 

 the tyrapanuni undergoes no change of function from the Amphibia 

 to the Sauropsida and Mammalia; it always remains in the service of 

 audition. — 2) The persistence of the hyomandibular-mandibular con- 

 nexion (acquired already by Elasmobranchs) in the shape of a connexion 

 of the extracolumella with the articulation in Crocodiles, Lizards and 

 Birds, or of the malleus with Meckel's cartilage in Mammalia. This 

 connexion is at first cartilaginous, later on merely ligamentous, even- 

 tually vanishing. — 3) The transformation of the quadrate into the os 

 tympanicum, intimately correlated with the acquisition of a new man- 

 dibular joint, the initial stages of which are demonstrated by Sauro- 

 psida, while truly Reptilian stages are still passed through by Mam- 

 malia. — 4) The satisfactory explanation, hitherto the only one, of the 

 posterior angle of the Mammalian jaw, inner or inverted angle of the 

 Marsupials. — 5) The possibility of refuting every objection to this view 

 by the production of facts without resorting to a priori hypotheses. 

 Such objections are the various instances of apparent discontinuity in 

 the phylogeny, or certain freaks. For instance the side-departure of 

 the recent Amphibia. The absence of a cartilaginous extracolumellar- 

 mandibular connexion in Sphenodon, the very Reptile in which we had 

 an a priori right to expect the persistence of such a connexion, whilst 

 in reality there is only a somewhat doubtful ligament. The difficulty 

 in finding a creature in which, at least during some stage of its onto- 

 geny the top end of the hyoid starts from the lateral end of the colu- 

 mella and medially from the extracolumella. 



But what about the other view which puts malleus = articulare, 

 incus = quadrate, tympanicum == quadrato-jugal? We are not told 

 what becomes of the extracolumella. Is it reduced to the lentiforme, 

 or does it sever its connexion with the Reptilian columella, bend down- 

 wards and become the manubrium of the malleus? This is Kingslet's 

 homology, who sees in the extracolumella or manubrium "the remains 

 of a visceral arch which has almost entirely disappeared from between 

 the hyoid and the mandibular arches". This is the latest discovery 

 we owe to ontogenetic research. A new visceral arch in Sauropsida 

 and Mammals! He has at least tried to give an explanation of, and 

 to make use of, the existence of the cartilaginous connexion between 

 the extracolumella and mandible in Sauropsida. The other apologists 

 of the articulare = malleus view are in no better plight. They shirk 

 the explanation of that retro-mandibular cartilage of Sauropsida, they 

 ignore the almost identical conditions of Crocodilia and Mammalia 

 and would of course be at a loss to give an understandable reason 



