192 



MARINE BIOLOGICAL LABORATORY. 



Leaving out of consideration all other developmental 

 processes connected with the completion of the auditory 

 organ, such as its enclosure in mesodermic tissue which 

 solidifies to form the ear-capsule (the bony labyrinth 

 of the adult ear of higher forms), I wish to call your 

 attention to two points of great importance for the cor- 

 rect understanding of the morphology of the ear. 



Torbedo .,, 



loccidenTali 



Fig. I. — The left internal ear of Tor- 

 pedo occidentalis dissected out of its 

 cartilaginous capsule, and viewed 

 from the outside. The somewhat dia- 

 grammatic figure represents the ear 

 about twice its natural size, as found 

 in a fish five feet in length. 



A"' Anterior ampulla. 



A*' Anterior canal. 



ac Auditory nerve. 



c.e Endolymphatic canal. 



CO Utriculo-saccular cone. 



H^ External ampulla. 



//< External canal. 



mu Macula utriculi duct. 



/ Lagena and papilla lagenae. 



P Surface pore of endolymph canal; jits 



sac. 

 P* Posterior ampulla. 

 Pt Posterior canal. 

 SC Sacculus and its macula sacculi. 

 U' and U" Utriculus and utriculo-saccular 



chamber. 



\lu* O.C 



I St. The ear vesicle does not divide, as previous 

 investigators have supposed, into superior and inferior 

 portions, but into an anterior and a posterior chamber. 



2d. The semicircular canals are not given off from 

 the utriculus alone, but from the saccnlus as well. With 

 these two misconceptions corrected, the way is clear 

 which leads to the really simple-as-the-truth account of 

 the morphology of the vertebrate ear, and we shall never 

 again encounter an auditory labyrinth. 



