882 



SCIENCE. 



[N. S. Vol. XI. No. 284. 



with the functions of organs, particularly of 

 the organs of the higher animals, is fre- 

 quently spoken of as Physiology, and sepa- 

 rated more or less sharply from the rest of 

 Zoology under that heading. So strong is 

 the line of cleavage between the work of the 

 Physiologist and that of other Zoologists, 

 that this Association has thought it advisa- 

 ble to establish a special Section for the dis- 

 cussion of physiological subjects, leaving the 

 rest of Zoology to the consideration of the 

 old-established Section, D. In calling at- 

 tention to this fact, I do not for one mo- 

 ment wish to question the advisability of the 

 course of action which the Association has 

 taken. The Science of Physiology in its 

 modern aspects includes a vast body of facts 

 of great importance and great interest which 

 no doubt require separate treatment. But 

 what I do wish to point out is that it is 

 quite impossible for us here to abrogate all 

 our functions as physiologists. Some of the 

 most important problems of the physiolog- 

 ical side of Zoology still remain within the 

 purview of this Section. 



For instance, the important and far-reach- 

 ing problems connected with reproduction 

 and variation are very largely left to this 

 Section, and that large group of intricate 

 and almost entirely physiological phenom- 

 ena connected with the adaptations of or- 

 ganisms to their environment are dealt with 

 almost exclusively here. Indeed, we may 

 go further, and say that apart altogether 

 from practical questions of convenience, 

 which make it desirable to separate a part 

 of physiological work from the Zoological 

 Section, it is, as a matter of fact, impossible 

 to divorce the intelligent study of structure 

 from that of function. The two are indis- 

 solubly connected together. The differen- 

 tiation of structure iuvolves the differenti- 

 ation of function, and the diiJerentiation of 

 function that of structure. The conceptions 

 of structure and function are as closely as- 

 sociated as those of matter and force. A 



zoologist who confined himself to the study 

 of the structure of organisms, and paid no 

 attention to the functions of the parts, would 

 be as absurd a person as a philologist who 

 studied the structure of words and took no 

 account of their meaning. In the early part 

 of this century, when the subject matter of 

 zoology was not so vast as it is at present, 

 this aspect of the case was fully recognized, 

 and one of the greatest zoologists of the 

 century, whether considered from the point 

 of view of modern anatomy, or of modern 

 physiology, was Professor of Anatomy and 

 Physiology at the University of Berlin. 



Having said that much as to the various 

 aspects of living ISTature, of natural history, 

 if you like, which it falls within the province 

 of this Section to deal with, I may now pro- 

 ceed to the subject of my address. And 

 when I mention to you what that subject is, 

 you will be able to make some allowance for 

 the somewhat commonplace remarks with 

 which I have treated you. For that subject, 

 though it has its important morphological 

 aspects, is in the main a physiological one; 

 at any rate, no study which does not take 

 account of the physiological aspect of it can 

 ever hope to satisfy the intellect of man. 



The subject, then, to which I wish to 

 draw your attention at the outset of our 

 proceedings, is the great subject of Variation 

 of Organisms. 



As everyone knows, there is a vast num- 

 ber of different kinds of organisms. Each 

 kind constitutes a species, and consists of 

 an assemblage of individuals which re- 

 semble one another more closely than they 

 do other animals, which transmit their 

 characteristics in reproduction and which 

 habitually live and breed together. But the 

 members of a species, though resembling 

 one another more closely than they resem- 

 ble the members of other species, are not 

 absolutely alike. They present differences, 

 differences which make themselves apparent 

 even in members of the same family, i. e., in 



