IQO MARINE BIOLOGICAL LABORATORY. 



possible the comparison of the embryonic conditions 

 with the adult, and the establishing of important phylo- 

 genetic conclusions based on these relations. 



John Beard first clearly saw the relation existing 

 between the sense-organs on the surface of the body 

 and the organ enclosed within the head by the for- 

 mation of the auditory vesicle (the auditory labyrinth 

 of the adult), but he failed to apprehend the nature of 

 the involution and the relation of the sense organ to its 

 walls. 



E. P. Allis, by giving us the first thorough investi- 

 gation of the relations of the sense-organs of the lateral 

 line system to the surface of the body, in the account 

 of which he describes the method of their enclosure 

 within canals, the laws of their increase, and of the 

 fusion and division of canals, the process of their sink- 

 ing below the surface of the body, and of their enclosure 

 within the cartilage (or the bone) of the skeleton, — 

 made known the developmental plan according to which 

 not only the superficial canal sense-organs grow and 

 reach their adult relations, but also, as it is now dis- 

 covered, the plan according to which the ear sense-orga7i 

 divides and forms its canals and other parts. This 

 latter fact is demonstrated by the published results of 

 numerous embryological investigations on animals from 

 the several classes of vertebrates. 



In order that we may fully recognize the influence 

 these investigations have had on the solution of the 

 problems concerning the phylogenetic history of the 

 human internal ear, it will be necessary first of all to 

 understand the anatomy of the ear in some type form. 

 For this reason I ask your forbearance while I briefly de- 



