758 REPORT—1899. 
logical 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 
indissolubly connected together. The differentiation of structure involves the 
differentiation of function, and the differentiation of function that of structure. 
The conceptions of structure and. function are as closely associated 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 recognised, and one of the greatest zoologists of the century, whether con- 
sidered 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 Nature, of natural 
history, if you like, which it falls within the province of this Section to deal with, 
I may now proceed 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 every one knows, there is a vast number of different kinds of organisms. 
Each kind constitutes a species, and consists of an assemblage of individuals which 
resemble 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 resemble the members of other species, are not absolutely alike. They pre- 
sent differences, differences which make themselves apparent even in members of 
the same family, z.c. in the offspring of the same parents. It is these differences 
to which we apply the term variation. The immense importance of the study of 
variations may be judged from the fact that, according to the generally received 
evolution theory of Darwin, it is to them that the whole of the variety of living 
and extinct organisms is due. Without variation there could have been no pro- 
gress, no evolution in the structure of organisms. If offspring had always exactly 
resembled their parents and presented no points of difference, each succeeding 
generation would have resembled those previously existing, and no change, whether 
backwards or forwards, could have occurred. This phenomenon of genetic varia- 
tion forms the bedrock upon which all theories of evolution must rest, and it is 
only by a study of variations, of their nature and cause, that we can ever hope to 
obtain any real insight into the actual way in which evolution has taken place. 
Notwithstanding its importance, the subject is one which has scarcely received 
from zoologists the attention which it merits. 
Though much has been written on the causes of variation, too little attention 
has of late years been paid to the phenomenon. Since the publication of Darwin’s 
great work on the ‘ Variation of Animals and Plants under Domestication,’ there 
have been but few books of first-rate importance dealing with the subject. The 
most important of these is Mr. William Bateson’s work, entitled ‘ Materials for 
the Study of Variation.’ I have no hesitation in saying that I regard this work as 
a most important contribution to the literature of the Evolution theory. In it 
attention is called, with that emphasis which the subject demands, to the supreme 
importance of the actual study of variation to the evolutionist, and a systematic 
attempt is made to classify variations as they occur in Nature. In preparing this 
book Mr, Bateson has performed a very real service to zoology, not the least part 
of which is that he has made a most effective protest against that looseness of 
speculative reasoning which, since the publication of the ‘Origin of Species,’ has 
marred the pages of so many zoological writers. 
The Variations of Organisms may be grouped under two heads, according to 
