32 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 57. 



known, may be thus summarized: (1) for each entire ramus there 

 is at first a cartilaginous matrix, mold, or bar (Meckel's cartilage), 

 continuous with the base of the skull and around wliich the dentary 

 and splenial bones are developed; (2) to this main cartilage there is 

 attached, or at least in intimate relation with it, an accessory cartilag- 

 inous mold or matrix, which gives rise to the condylar portion; (3) 

 the anterior part of Meckel's cartilage is entirely converted into that 

 part of the dentary lying between the mental foramen and the sym- 

 physis, which is therefore true cartilage bone; (4) the posterior por- 

 tion of the dentary arises from the backward extension of the perichon- 

 drium surrounding the cartilage, but the cartilage itself does not 

 undergo ossification but absorption; (5) the splenial is developed from 

 the same perichrondrial membrane as the posterior portion of the 

 dentary; and (6) the cartilaginous molds preceding the coronoid and 

 condyloid portions either ossify from separate centers (according 

 to Tiiompson) or receive then ossific deposits by means of a ])osterior 

 prolongation of the perichondria! membrane from the dentary. 



Now, what can we learn from these facts and what bearing do they 

 have upon the triinsposition theory as a whole, and the homology 

 of the articular with the malleus in particular ? If Thompson's state- 

 ment in regard to a separate center of ossification for the condyloid 

 portion of the human jaw is correct, then the whole matter is settled 

 and requires no further discussion; for in that event this ossification 

 would represent the articular of the reptilian jaw beyond all reason- 

 able doubt. But if we allow that this statement is erroneous and is 

 not borne out by the facts, we have remaining the all-important 

 feature or circumstance, about which there can not be the least 

 doubt or uncertainty, that a cartilaginous mold or matrix, in inti- 

 mate association with the Meckelian cartilage, is always present and 

 precedes in the order of development the purely secondary or subor- 

 dinate process of deposit of calcareous matter in this part of the carti- 

 laginous ramus. As between the presence of this cartilaginous mold 

 and tlie secondary process of its calcification, in morphological im- 

 portance, there can be no question or argument whatever. 



If this strict homologue or corresponding part of the reptilian or 

 batrachian jaw has been bodily plucked out and removed to another 

 situation, with a completely altered function in the mammal, then 

 it is utterly inconceivable to me and entirely passes my understand- 

 ing to imagine how this could have been accomplished without taking 

 along with it the morphologically fundamental part of which it pri- 

 marily consists. That this portion should liave been left behind in 

 its original and primitive position is to my mind more than signifi- 

 cant. The burden of proof lies with those who maintain the trans- 

 position view, and if this difficulty can not be completely removed 

 or explained, they can not only have no standing in court but the 



