SEVENTH LECTURE. 



BDELLOSTOMA DOMBEYI, LAC. 



A STUDY FROM THE HOPKINS MARINE LABORATORY. 



PROBLEMS in Biology are inexhaustible, they renew them- 

 selves continually. They appear with kaleidoscopic changes 

 to successive generations of men, who receive them to study 

 in new light and from new standpoints. The results of these 

 studies are not all as stable as the problems themselves. 

 These results present themselves to us as facts, and as theories 

 based on facts. Although one well-established fact is worth 

 much speculation about its significance, yet, without the aid 

 of well-considered theories concerning the causes which lie 

 back of the facts and the meaning of the facts in themselves, 

 progress were well-nigh impossible. 



These are trite sayings, but they have very appropriate 

 applications to the problems of the nature and functions of 

 the ear at the present time. The general problems of the 

 morphology and physiology of the vertebrate ear are much 

 the same as they were when first taken up, for the two ques- 

 tions, "How is the vertebrate ear constructed?" and "How 

 does it operate?" still express the aims of our researches in 

 this field as well as they did when man first began to study 

 into his auditory anatomy. But our conception of the manner 

 in which these problems are to be solved at the present day is 

 no longer what it was fifty years ago, or, indeed, ten years ago. 

 We now appreciate the full force of the requirements which the 

 present condition of morphological and physiological science 

 demands in the investigation of these problems. To know 

 the structure and function of our own ear, we find it not only 

 necessary to study the adult anatomy and function of the ear 

 in man, but also in every other vertebrate form as far as pos- 



