4 AVERS. [Vol. VI. 



canals as progressing in a manner practically identical in the 

 Teleost ear. The conviction at once forced itself upon me that 

 since we find in the development identical mechanical processes 

 on the surface of the body and within the ear, resulting in 

 similar structures, viz. the enclosing canals of the sense organs, 

 the ear canals must be genetically related with the surface 

 canals; for my own observations had just shown me that, in 

 two forms at least, the internal ear was a sense organ taken 

 out of a group, the remainder of which is enclosed within the 

 so-called aural canal, near its junction with the occipital and 

 lateral, as I shall describe more fully and with figures further 

 on. Beard ascribed this earlier inclosure of the auditory organ 

 to the fact that the hairs on the auditory cells are concerned 

 in the perception of much finer wave motions than the super- 

 ficial sense organs, viz. sound waves alone ; and he concludes 

 {loc. cit. p. 143), " In accordance with, and as a direct conse- 

 quence of, this function of receiving waves of sound, the audi- 

 tory organ has been early shut off from the external surface, 

 and has developed accessory structures in the shape of semi- 

 circular canals, etc. Thus its primitive simplicity has been lost!' 

 I shall endeavor to show that there is no change in the plan of 

 structure of the auditory organ as it grows towards its adult 

 condition, and that there is no more a loss of its "primitive 

 simplicity " than in the case of the superficial sense organs, 

 which, by dividing, produce several or many organs, and where 

 they are ca7ial organs, concomitantly bring about the produc- 

 tion of a canal complex made up of a number of simple homo- 

 dynamous units, each related to its fellows according to a simple 

 and symmetrical plan. We need no longer think of the ear as 

 a complicated labyrinthine structure, but rather as a symmetrical 

 group of organs. 



Although Beard's paper marked a great advance, we were 

 still without clue to the significance of the peculiar and strik- 

 ingly characteristic structures of the internal ear of vertebrates 

 and the older view which Hasse advanced and defended ; viz. 

 that there is a complete agreement between the early stages in 

 the development of the vertebrate ear and the invertebrate 

 auditory organs, and that the former had arisen out of the latter 

 by a transformation of its walls and chambers, was still, if not 



