i6 



A VERS. 



[Vol. VI. 



thread between the two structures. The endeavors of anatomists 

 to arrange the canals under a common type have not proved 



fruitful, for the reason that no 

 such relations exist between the 

 canals and the other parts as 

 has been supposed. Each canal 

 is an individuality whose charac- 

 ters, so far as shape, size, and 

 spatial relations, are not con- 

 nected in any special way with 

 the corresponding characters of 

 its neighbors. In its develop- 

 ment each canal takes such 

 shape and relations to other 

 parts as its surroundings per- 

 mit. They are 7iot developed as 

 specially functional structures, and their relations may well be 

 a matter of no account to the animal. As we shall see further 



Cut 5. — The horizontal canal of 

 the same ear projected in the sagit- 

 tal plane. 



Cut 6. — A projection of the semicircular canals of a Galeus canis five feet in 

 length on the horizontal plane, to show their angular relations to the sagittal plane 

 and to each other. No allowance is made for the curvature of the canals in their 

 proper planes. Natural size. 



on, two of them are related as parent and offspring, descended 

 from the utriculus, while the remaining posterior canal is a 

 descendant of the sacculus. 



