No. I.] THE VERTEBRATE EAR. 13 



no means semicircular in shape, nor are they placed at right 

 angles to each other. 



The planes in which the canals for the most part He are not 

 parallel with the three planes of the animal's body ; viz. the 

 sagittal, transverse, and horizontal respectively. 



The extent of the variations from these three planes are shown 

 in Cuts 2-6. The anterior vertical canal ca., as seen from above, 

 bends caudad in its distal portion, and cephalad in its proximal 

 portion ; its plane cuts the sagittal plane of the body at an 

 angle of 50°. The angle included between it and its fellow, the 

 posterior vertical canal icp), is not 90°, but only 82°. The angle 

 at which the posterior vertical canal cuts the sagittal axis of 

 the body is consequently 48°, and it does not coincide with any 

 transverse plane passed through the body. It is thus seen that 



Cut 2. — A projection of the semicircular canals of the ear of the Torpedo occi- 

 dentalis on the horizontal plane, to show their angular relations to the vertical 

 (sagittal) plane. 



the vertical canals do not lie in planes parallel with two axial 

 planes of the body, respectively, the sagittal and the transverse, 

 as is commonly supposed. The so-called horizontal canal, or, as 

 I prefer to designate it, the external, does not lie in a plane 

 parallel with the horizontal plane of the body, but always, as I 

 have found it, inclined in two directions to that plane. The 

 usual arrangement is presented by the Torpedo where the plane 

 of this canal inclines downwards and forwards from the hori- 

 zontal. 



On comparing the various canal-forms found among verte- 

 brates, one is struck by the great variety presented. The 



