aoe) oF 
D.—ZOOLOGY. 121 
lation of its place in nature, ‘choice’ of environment (including the 
presence of other organisms as well as the conditions of life in the restricted 
sense), adherence to a selected field of outer impulses, constitute an 
essential feature in that relatedness which constitutes individuality. ‘1 
am part of all that I have met.’ 
A few illustrations taken from recent ecological work may not be un- 
welcome. Mr. Eliot Howard (13) has concluded that spring migrants to 
England each after their kind select and guard a territory on their arrival. 
The distinctive song of the cock announces this achievement to the later 
flight of silent passing hens, and mating is but a prelude to a continuous 
policing of the stretch of hedge, area of moor, or piece of covert whose 
boundaries, to us invisible, are clear to them. The intrusion of another 
cock of the same species ishotly resented, and fierce engagements, extended 
it may be, to the cocks and hens of other species, are continued, up to the 
boundary and then suddenly cease. The bird and its environment—the 
territory—have become one activity, and it is restless till it hasestablished 
itself in its niche. Just so, to take a more familiar example, each member 
of a Council or Parliament at each sitting has to regain his orientation 
both to place and to person before he can be at rest and at his best. 
As J. S. Haldane has put the matter, ‘regulation of the external en- 
vironment is only the outward extension of regulation of the internal 
environment . . . An organism and its environment are one’ (14, 
p- 99). 
If we now apply the principle of physiological isolation to the organ- 
ism as influenced by, and influencing, its external environment, many well- 
known facts of zoological distribution become intelligible. Isolation arises 
from many different causes—by isolation by growing size, by decrease 
in conductivity in the path of transmission from the dominant region, 
by decrease in dominance itself, or to a change in the conditions of life— 
and no general statement can be made that will cover all cases. 
Bearing in mind, however, that life under dominance tends to exhaustion, 
whereas isolation leads to the renewal of activity at a lower level of 
complexity, we should be prepared to find that organisms change their 
environment with change in their physiological conditions, and that 
historically there would be ‘ backwaters’ of those stocks that represent 
ancient stages of more progressive races; and we should further expect 
that these ‘islands’ would possess a higher metabolic rate than the more 
differentiated and highly integrated races. To them rather than the domin- 
ant races we should expect the future to belong. From others, like them 
externally perhaps, we should expect neither progress nor repression, but 
a balance that, indefinitely perhaps, postpones the evil day. 
These relations we do find. The indefinite persistence of Lingula and 
Nautilus on the mud flats and depths of the Fijis in the Far Hastern seas, 
of Pleurotomaria in the Far East and West, the general isolation of * living 
fossils,’ is on this view to be regarded as a balanced senescence. Even in the 
most progressive regions of the world there are islands or backwaters 
where such arrested balance maintains a precarious existence. Proteus 
and other primitive forms survive only in the Balkan peninsula. Primitive 
societies of mankind or primitive customs likewise survive in those isolated 
‘communities of a progressive race. Modern industrialism creates such 
islands where the raw material or the working conditions demand isolation 
