No. 2304. REPTILIAN CHARACTERS IN MAMMALS— WORT MAN. 41 



continue to hold that Gadow's objection constitutes a fatal and insup- 

 erable impediment to tliis impossible hypothesis. 



If the facts and arguments above set forth are not sufficient to 

 completely disprove the transposition theory, there is yet another, 

 and I shall conclude the discussion of this subject by directing atten- 

 tion to a body of evidence which I regard as the most important and 

 conclusive of all. Did this evidence stand alone without the support 

 of the facts hereinbefore mentioned, it would be amply sufficient in 

 itself to utterly annihilate and destroy any possibility of the truth 

 of this hypothesis. It may be stated as foUov.'s: Huxley in his 

 treatise on the anatomy of the Amphibia, in describing the skull 

 of Rana esculenta says: ^ 



The slender permanently cartilaginous hyoidean cornu passes into the cartilage of 

 the auditory capsule on the ventral side, between the fenestra ovalis and the articu- 

 lar surface for the crus of the suspensorium. The fenestra ovalis lies in a cartilaginous 

 interspace between the exoccipital and the prootic and is filled by the oval cartilagi- 

 nous stapes. The anterior face of this presents a concave facet for articulation with 

 a corresponding surface occupying the posterior half of the inner end of the columella 

 auris, the anterior half of which fits into a fossa of the prootic bone. The columella 

 itself consists of three portions, a middle elongated osseous rod, an inner swollen car- 

 tilaginous part, wliich articulates with the prootic and partly with the stapes, and 

 an outer portion, which is elongated at right angles to the rest, fixed into the tympanic 

 membrane and attached by its dorsal end to the tegmen tympani. 



What more completely homologous arrangement of the several 

 parts of this auditory apparatus, as well as the homologies of the 

 elements themselves, with that of the mammal could possibly be 

 asked for? The essential pomts of similarity are seen in (1) that 

 the proximal end of the hyoidean arch does not join the auditory 

 capsule through the intermediation of the stapes or the columella, 

 as in birds and reptiles, but is joined directly to it as in the mammals; 

 (2) that the auditory chain consists of four main elements, nam^ely: 

 a cartilaginous stapes, a swoUen cartilaginous inner end of the 

 columella, a bony columella itself, and a cartilaginous portion fixed 

 into the t}Tnpanic membrane; (3) that the stapes is short and nod- 

 ular (mammalian) and not long and styliform (sauropsidan) ; (4) 

 the element articulating with the stapes next upon the outside also 

 articulates by a distinct facet with the prootic on the side wall of the 

 capside like that of a mammal and not like that of a reptile; (5) that 

 of the transverse cartilaginous element, upon the outside, the ven- 

 tral end is fixed into the tympanic membrane, and (6) that the ele- 

 ment lying next upon the inside forms a bony connection between 

 the last named piece and the base of the columella. 



In attempting to determine the homologies of these several ele- 

 ments of the auditory chain in Rana and those of a mammal, it is 

 not difficult to discover that the stajyes in the two is strictly homologous 

 heyond any shadovj of a doubt. In a like manner there can not be 



1 Encyclopedia Britannica. Ninth Edition, 1875, pp. 661, 662. 



