126 BIOLOGICAL LECTURES. 



sible. Nor can we stop here. We must trace out the ontogeny 

 of this organ in all those forms whose adult anatomy we 

 study, and in so doing apply the known laws of physics and of 

 chemistry to the development of their forms and contents. We 

 must trace out the phylogenetic development of the ear by the 

 comparative study of what we have gained from the above out- 

 lined investigations, combined with knowledge from two sources 

 yet untouched, viz., the morphology and physiology of those 

 sense-organs, genetically related to the ear sense-organs, and 

 the scanty store of facts pertaining to our problems which 

 palaeontology can give us. Investigations undertaken on a 

 basis less broad than this, or which do not fall within some 

 one of the categories above mentioned, are sure to fall far 

 short of the solution in the first case, and, in the second case, 

 to be of little or no service in the general progress toward the 

 final solution of these problems. 



It is thus made apparent, I think, that although the physio- 

 logical problem is not as extensive as the morphological, it is 

 not for that reason less difficult or more likely of an early solu- 

 tion, for its final solution depends quite as much upon our 

 advances in a knowledge of the anatomy and physiology of 

 the central nervous system as upon experiments upon the ear 

 itself. With this prospect of long-postponed final solution, 

 facts which have direct bearing upon any of the fundamental 

 topics of ear physiology, are all the more valuable. One such 

 fact I wish to announce, viz., that there is at least one verte- 

 brate which does not depend upon its internal ears for the 

 equilibration of its body. I had previously concluded that the 

 semi-circular canals were not organs of equilibration, and inci- 

 dentally during my anatomical work I was able to determine 

 that the ear of this vertebrate is in no way more concerned in 

 maintaining the position of its body in space than are the other 

 sense organs. 



In the lectures for 1891, I brought to your attention certain 

 facts and arguments to illustrate the gradations of structure 

 of the ear found among vertebrate animals, which have led up 

 to the production of the human ear. And I showed the man- 

 ner in which the ear of Marsipobranch fishes presents us with 



