SOUND-TRANSMITTING APPARATUS OF CAUDATA 365 



these movements must have been may be appreciated by recall- 

 ing the waddling gait of a walking fish and the crawling gait of 

 a modern salamander. The transitional amphibian must have 

 possessed a mode of locomotion which would fall between these 

 two extremes, in which case the jaws and branchial apparatus 

 rested upon the substratum for a large portion of the time. The 

 lateral line sense becoming functionless as the animal left the 

 water, and hearing, if it existed in a refined state, certainly be- 

 coming much impaired, left these transitional amphibians with 

 no special means of communication between the inner organism 

 and disturbances which might occur in the surroundings. The 

 relation of the jaws to the substratum, through contact, and to 

 the auditory capsule, through the hyomandibular and its liga- 

 ments, formed a natural pathway for the transmission of vibra- 

 tions. Thus, for physical reasons alone, it can be understood 

 how the columella represents a refined hyomandibular and how 

 the fenestra vestibuli may have come about. The structural 

 supports for this view and the importance of such hyomandibular 

 relations as are found in the notidanid sharks were discussed by 

 Kingsbury and Reed ('09). 



Accepting the general view that the larval period represents 

 a more recent interpolation in the life-cycle of amphibians, one 

 observes that the gait and relations of the body to the sub- 

 stratum of a modern larva is undoubtedly like that of the earliest 

 amphibian forms, and that the demands upon the columella of 

 the recent larvae are unquestionably no different from those made 

 upon this structure in the primitive estate when amphibians were 

 slowly evolving from fish-like forms. Since the columella was 

 the first of the sound-transmitting elements to appear in phy- 

 logeny, it is quite natural that it should persist and function dur- 

 ing the larval period of recent salamanders, although this period 

 is a later addition to the life-cycle. It follows, then, that, in 

 aquatic species such as the Cryptobranchidae the columella 

 alone does not indicate the phyletic relations of its possessor, 

 and one must look further into the morphology of these animals 

 in order to determine their true rank. 



