THE AM ERIC AX NATURAUST. [Vol. XXXVII. 



vertebrates. It is thus evident that the sense of hearing is 

 coupled with high organization. 



When a survey of the whole animal kingdom is made, it is 

 found that most sense organs arc not restricted as the organs of 

 hearing are ; for instance, eyes, often of a complicated structure, 

 occur in such lowly organized animals as jellyfishes, starfishes, 

 and worms, and these animals react with great precision to light. 

 Not only do many of these lower animals possess eyes, but they 

 also have organs of touch, taste, etc. ; in fact, the only important 

 sense organ lacking in them is that of hearing. Since the sense 

 of hearing is found only in the more highly organized animals 

 and the other senses occur in the lower as well as in the higher 

 animals, it follows that hearing is probably the most recently 

 acquired of the senses. 



If in accordance with these facts we endeavor to form some 

 idea of the evolution of the sense organs in the animal series, we 

 must picture to ourselves an early origin for all the important 

 senses except hearing. This sense was undoubtedly the last 

 important one to be differentiated and the reason for the lateness 

 of its appearance I hope to make clear to you toward the close of 

 this lecture. 



It is a remarkable fact that the ear in the higher vertebrates, 



perfection of the human eye and this organ undoubtedly dis- 

 plays a marvelously delicate construction, but in my opinion the 

 efficiency of the ear as an organ of sense is as much beyond that 

 of the eye as a modern chronometer is beyond an old-fashioned 

 sundial. Kvidence of the truth of this opinion can be seen in 

 the many defects that are present in the eye as contrasted with 



Thus, when red light is'combined with bluish green, the result- 

 also yellow and violet, green and pink, etc. To all these com- 

 binations, which are totally distinct from a physical standpoint, 

 the eye answers with but one sign, that for white light. 



Color in light corresponds to pitch in sound, for both depend 



