^^ derwed from upper iav\» 

 (tirst qiM orch) 



^^ derived "from \o\wer jow 

 (first qill orcb) 



I^H derived from hyoid 

 (tonque) apparatus 

 (second qwl orch) 



numerals indicate oriqinol 

 q\\l orches 



coiumeiia 

 (stopes) 



molleus 

 (hammer) 



incus 

 (anvil) 



stopes 

 (stirrup) 



Fig. 25-11. The history of the gill arches indi- 

 cates that many changes took place be- 

 tween the shark and man, yet evidences of 

 the transition are clearly present. In the 

 shark the gill arches were used in breath- 

 ing water. In the frog the beginnings of 

 the sound-making apparatus have deveF- 

 oped and the sound-receiving apparatus 

 has been further perfected. A portion of the 

 hyoid (II) has become the columella, a fore- 

 runner of the stapes in the mammalian ear. 

 The frog has also made use of the remain- 

 ing gill arches in the formation of the laryn- 

 geal apparatus for the purpose of making 

 sound. 



In the mammal the sound-receiving and 

 making apparatuses have developed to a 

 high degree of perfection, but the origins 

 of the ear bones and the larynx are still 

 evident. 



, larynx _ 

 (voice box) 



Irachea 



