No. I.] THE VERTEBRATE EAR. 311 



which stimulated the nerves by compressing them or delivering 

 suitable blows on or near the ends of the fibres. 



16. The membrana basilaris is far too complex a structure to 

 permit of its use as a vibrating membrane capable of responding 

 in its various parts quite independently to sound stimuli of vary- 

 ing wave lengths. 



The membrane is composed of several superposed sheets of 

 fibres and adnexed cell masses, and, as I have recently dis- 

 covered, there is also a special vascular layer (Sus, Bos) or sys- 

 tem of basilar capillary loops, which layer is placed between the 

 fibrous layers and for the most part below the nerve fibre layer 

 of the inner border of the membrane. This vascular layer is 

 composed of numerous circuitous capillary channels which have 

 been overlooked by previous investigators. The basilar mem- 

 brane cannot possibly meet the physical demands made upon it 

 by the Hensen-Helmholtz "piano-string" theory, and, as I have 

 shown, its phylogenetic history proves it to be a modified por- 

 tion of the skin of the head which forms first and last the floor 

 upon which the sense organs rest. 



17. If the ear originated from surface canal organs and their 

 inclosing canals, it became evident that the older view of the 

 segmental value of the so-called VIII or auditory nerve could 

 not be true ; if the view of the morphological value of the VIII 

 was indeed true, then the origin of the ear from surface canals 

 could not be true in the sense claimed ; consequently this 

 apparently fatal objection must be removed. An examination 

 of the present state of our knowledge of the auditory nerve 

 supply, together with a few additions I have been able to make 

 to the subject of the innervation of the auditory sense organs 

 in the Cyclostomes and Elasmobranchs, proves conclusively 

 that throughout the vertebrate group the same plan of inner- 

 vation is maintained which is laid down in the Cyclostomes and 

 that a dual peripheral origin and a dual central termination of 

 the auditory nerve fibres in intimate connection with the VII 

 and IX respectively, is the first fundamental fact of ear nerve 

 supply. The ear organs are innervated by the nerves which 

 supply surface canal sense organs. The genetic relationship 

 of the VII and IX nerves to the VIII is shown by the entrance 

 of the parental nerves into the auditory capsule, where they both 

 give off nerve branchlets to supply ear sense organs and then 



