38 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.57. 



if not completely destroying, the bearing, has never been met by the 

 advocates of this view. Gregory attempts to reply to this objection 

 in the following statement: * 



Dr. Broom, in a letter to the writer dated July 20, 1911, wrote that he had decisive 

 evidence showing that the doubted element is stapes and not tympanic. In Broom's 

 figure ('11, p. 7, pi. 46, fig. 8) of the very primitive Cynodont Bauria this supposed 

 stapes runs out toward the quadrate. Its distal end is imperfect, but Broom restores 

 it in contact with the quadrate. The stapes is represented as reaching nearly or 

 quite to the quadrate in Cynognathus (Broom, '04, pp. 490-498, pi. 25) and Oudenodon 

 (Broom), Dimetrodon (Case), Labidosaurus (Williston), as well as in modern snakes, 

 chameleons, tortoises, and some urodeles (Kingsbury and Reid) and caecilians 

 (Kingsley). If, as now appears probable, the stapes touched tlie quadrate in Cyno- 

 donts, then it is clear that stapes, quadrate, and articular already formed a connected 

 train of bones. Thus would be met Gadow's objection ('88) "that the incus can not 

 be the homologue of the qviadrate because of the impossibility of intercalating the 

 quadrate as an incus into the ossicular chain as a link between the stapes (h} oman- 

 dibula) and lenticulare (symplectic) and the malleus (articulare). " But the quad- 

 rate (incus) was not "intercalated " in the chain; it was there from the time that the 

 hyomandibular (stapes) became attached to it (p. 28). 



In just how far this statement constitutes an answer to Gadow's 

 objection we shall presently see. 



If we consider the subject from the broad standpoint of evolution 

 alone, there are so many serious objections that can be raised against 

 any such theory as to render it not only highly improbable but 

 quite impossible. When we reflect upon the important role the 

 function of hearing must always have played in the animal economy, 

 and liow necessary'' and vital it must have always been to those 

 animals of a terrestrial habitat, we are then prepared to understand 

 something of the nature of the evolution and development of this 

 delicate and highly complex apparatus, which we have every reason 

 to believe has taken untold generations to complete and perfect. As 

 its highest development is now found in mammals, in which 

 it is remarkably similar in all, we have a right to believe tliat the 

 promammalian reptiles or batrachians from which they were derived 

 had an auditory apparatus, wliich, while perhaps not as delicate and 

 finely fashioned as that of the mammal, must have, according to the 

 very nature of the case, approached it in delicacy, efhcienc}^, and fine- 

 ness of finish. There can be little doubt that it must have equaled at 

 least in effectiveness that of bhds or crocodiles living to-day, if it did 

 not surpass them in this regard. 



We may go even further than tliis and declare without fear of 

 orror that in all probability these promamm.alian reptiles, if, in- 

 deed, they were reptiles at all in the strict sense of tlie term, had 

 a rudiment of an external ear; that they had a highly developed 

 tjTupanic membrane stretched in front upon the quadrate, above 



' Critique of Recent Work on the Morphology of the Vertebrate Skull, Especially in Relation to the 

 Origin of Mammals, Journal of Morphology, vol. 24, Ko. 1. tfarch, 1913. 



