No. I.] THE VERTEBRATE EAR. i^y 



Vogt (1842 1) agrees with neither Valentine nor Rathke, but 

 was not certain that he had rightly interpreted the processes of 

 canal production. He thought they were produced by the 

 growth of the cartilaginous capsule forcing in the walls of the 

 auditory vesicle until the folds thus formed met and produced 

 the canals. He did not observe the development of the sensory 

 epithelial structures. 



Reissner (185 1, 228) and Rosenberg (1868, 242) agreed in all 

 essential particulars with Rathke. Their observations were 

 made on mammals. 



Boettcher (1869, 31) was the first accurately to describe the 

 origin of the two vertical canals in mammals from a common 

 furrow. 



Goette (1875^) described the development of the Amphibian 

 ear in his studies on Bombinater. And his account of the 

 development of the semicircular canals shows that they de- 

 veloped in the same manner as in mammals according to 

 Boettcher's account. 



Von Noorden (1883, 205) devotes much care to working out 

 the transformations of the auditory vesicle in bony fishes, and 

 by means of direct observations on the transparent living em- 

 bryo, by means of sections, and also by means of models recon- 

 structed from serial sections, he was able to give us the most 

 accurate as well as the most detailed account of the morphologi- 

 cal changes which the ear undergoes in development, that we 

 have of the Teleosts. His observations were made upon eight 

 species, including the European trout, salmon, and herring. 



Riidinger (1888, 244) returned to the old theory of Valentine, 

 This he somewhat modified. He says {loc. cit.) : 



" I. Die Bogengange entstehen durch epitheliale Knospung 

 oder Sprossung aus der Ohrblase. 



"2. Fur jeden einzelnen Bogengang treten zwei Sprossen auf. 



" 3. Die Vereinigung der beiden Sprossen kommt zu Stande 

 durch die Grossenunterschiede der Zellenmaterials an der con- 

 vexen und concaven Seite eines Bogengangs." Riidinger claims 

 to have found the canals in their first stages of growth as blind 

 pockets leading out of the utriculus. 



His (1889, 137) describes the formation of the canals in the 



1 Embryologie des Salniones. Neuchatel. 



2 Entwicklnngsgeschichte der Unke. Leipzig. 



