perilymi 



stapes 



perilymphatic canal 



lar papilla organ 

 amphibian papilla 



utriculus 

 endolymphatic 



lagena with basilar 

 ' papilla organ 



eustachian tube 



PRIMITIVE 



metotic fissu 



perilymphatic sac 

 AMPHIBIAN 



sacculus 

 eustachian tube 



TURTLE 



endolymphatic sac 



stapes 



endolymphatic 

 foramen 



perilymphatic 

 foramen 



metotic foramen 



LIZARD 



fenestra cochleae 

 metotic foramen 



MAMMAL 



Figure 13-22. Diagrammatic cross section through the otic capsules of several tetropods showing 

 the variations of inner ear and perilymphatic sac development. (After Cordier and Dolcq, 1945, 

 and Romer, 1955) 



and lagenar maculae (sensory areas) as well as a macula 

 neglecta (Figure 13-23). There are no otoliths or granules; 

 the currents within the utricular chambers appear to re- 

 place these. The endolymphatic duct is a short, closed tube. 

 In fossil osteostracans and heterostracans the inner ear has 

 two semicircular canals as in the lamprey. 



In the osteostracans the inner ear is associated with radi- 



ating canals which e.xtend out to dorsal and lateral fields. 

 Stensio viewed these fields as filled with electric muscle tis- 

 sue and the canals as occupied by the nerves for these 

 muscles. It has been pointed out that the fields are too 

 small to hold enough muscle to produce an effective shock, 

 therefore, it has been suggested that they were sensory fields 

 for reception of vibratory stimulae and that the canals were 



endolymphatic duct 



posterior crista 



posterior 

 semicircular canal 



posterior canal ampulla 



VIII 



MYXINE 



B 



LAMPREY 



utrlculus 



horizontal canal lagena 



D SQUALUS 



-endolymphatic duct 



horizontal canal 



utriculus' 



ampulla 



posterior vertical 

 semicircular canal 



endolymphatic duct 



macula neglecta 

 sacculus 



utriculus' 



sacculus' 

 macula neglecta 



endolymphatic sac 



macula neglecta 

 utriculus 

 sacculus 



HYDROLAGUS 



TELEOST 



ALLIGATOR 



H 



lagena 

 (cochlea) 



HUMAN 



Figure 13-23. Semidiogrommatic views of the left inner ear of several types of vertebrates. C is 

 a medial view; the others, lateral views. (In part after Neal and Rand, 1 936) 



SENSORY ORGANS 



409 



