No. 2304. REPTILIAN CHARACTERS IN MAMMALS— WORTM AN. 39 



upon the squamosal, and behind in the higher forms probably upon 

 a delicate, commencing tympanic bone, similar to that seen in the 

 peafowl among birds; that they had a capacious tympanic cavity, 

 provided with eustachian tube opening into the pharynx, a fenestra 

 ovalis and fenestra rotunda leading to the lab}Tinth; that across 

 this tympanic cavity was stretched a chain consisting wholly of 

 ■delicate bones or in part of cartilaginous elem.ents, one end of which 

 fitted into the fenestra ovalis and the other attached to tlie ear 

 <lrum, in order to conduct the sound \vaves or impulses of the tym- 

 panic membrane to the lympth of the labyrinth; and, lastly, that 

 the internal ear was provided v/ith its proper semicircular canals, 

 utricle, saccule, and cochlea, which may or may not have been 

 spirally coiled. 



Now, when we study the structure and function of this apparatus 

 in its higher development, whether it be in the mammal or the higher 

 Sauropsida, such as in the crocodile, in the birds, or even in the higher 

 Batrachia, as in the frog, we are forced to conclude that one of the 

 fundamental, essential, and all-important objects of its evolution 

 has been delicacy and fineness of finish. Tliis appears perfectly 

 obvious, for the reason that without this delicacy of structure the 

 finer sound waves could not be transmitted or recognized, and if 

 its possessor were in any way dependent upon such recognition for 

 any purpose whatever, then, in the event of its impairment, its 

 further evolution would have been arrested and would have imme- 

 diately ceased. If, on the other hand, we study the structure and 

 function of this apparatus in its more primitive stages or less perfect 

 manifestations, such as in the tailed Batrachia and many of the 

 living Reptilia, we can begin to understand through what steps 

 or stages it arose in the higher or more developed tj^pes. Thus, in 

 all Batrachia except frogs there is no tympanic cavity and no tym- 

 panic membrane. There is no fenestra rotunda, and the internal 

 «ar is altogether primitive. In snakes and Amphisbaenoids there 

 is no tympanic cavity nor tympanic membrane. In many Chelonia, 

 in S'pJienodon, and chameleons the tympanic membrane is covered 

 with integument, etc. All of these facts, as well as many others 

 that could be mentioned, simply go to show how the more perfected 

 ■development has been brought about. 



Another fact to be mentioned in this connection is that in all the 

 lower types of structure of this hearing apparatus the quadrate is 

 always present and strongly developed and acts as a suspensorium 

 of the lower jaw, just as is the case with the articular, the element 

 by means of which it is hinged or articulated with the mandible. 

 But at the same time it must not be concluded that a delicate hearing 

 apparatus is not consonant nor consistent with the presence and 

 full development of these bones, for in birds a well-developed quad- 

 rate and articular are present and in their usual positions, and the 



