SCIENCE. 
267 
THE UNITY OF NATURE. 
By the Duke of Argyll. 
III. 
ANIMAL INSTINCT IN ITS RELATIONS TO THE MIND OF MAN. 
The Dipper or Water-ousel ( Cinclus aquaticus) is well 
known to ornithologists as one of the most curious and in- 
teresting of British birds. Its special habitat is clear moun- 
tain streams. These it never leaves except to visit the lakes 
into which or from which they flow. Without the assistance 
of webbed feet, it has extraordinary powers of swimming 
and of diving — moving about upon and under the surface 
with more than the ease and dexterity of a fish — hunting 
along the bottom as if it had no power to float — floating on 
the top as if it had no power to sink — now diving where the 
stream is smooth, now where it is quick and broken, and 
suddenly reappearing perched on the summit of some pro- 
jecting point. Its plumage is in perfect harmony with its 
haunts — dark, with a pure white breast, which looks exactly 
like one of the flashes of light so numerous in rapid streams, 
or one of the little balls of foam which loiter among the 
stones. Its very song is set to the music of rapid waters. 
From the top of a bank one can often get quite close to it 
when it is singing, and the harmony of its notes with the 
tinkling of the stream is really curious. It sings, too, when 
all other birds but the Robin is silent — when the stones on 
which it sits are circled and rimmed with ice. No bird, per- 
haps, is more specially adapted to a very special home and 
very peculiar habits of life. The same species, or other 
forms so closely similar as to seem mere varieties, are found 
in almost every country of the world where there are moun- 
tain streams. And yet it is a species having no very near 
affinity with any other bird, and it constitutes by itself a 
separate genus. It is therefore a species of great interest to 
the naturalist, and raises some of the most perplexing ques- 
tions connected with the “origin of species.” 
In 1874 a pair of these birds built their nest at Inverary, 
in a hole in the wall of a small tunnel constructed to carry 
a rivulet under the walks of a pleasure ground. The season 
was one of great drought, and the rivulet, during the whole 
time of incubation and of the growth of the young in the 
nest, was entirely dry. One of the nestlings, when almost 
fully fledged, was taken out by the hand for examination, 
an operation which so alarmed the others that they darted 
out of the hole, and ran and fluttered down the tunnel to- 
wards its mouth. At that point a considerable pool of water 
had survived the drought, and lay in the paths of the fugi- 
tives. They did not at all appear to seek it ; on the con- 
trary, their flight seemed to be as aimless as that of any 
other fledgeling would have been in the same predicament. 
But one of them stumbled into the pool. The effect was 
most curious. When the young bird touched the water, 
there was a moment of pause, as if the creature were sur- 
prised. Then instantly there seemed to wake within it the 
sense of its hereditary powers. Down it dived with all the 
facility of its parents, and the action of its wings under the 
water was a beautiful exhibition of the double adaptation to 
progression in two very different elements, which is pecu- 
liar to the wings of most of the diving birds. The young 
dipper was immediately lost to sight among some weeds, 
and so long did it remain under water, that I feared it must 
be drowned. But in due time it reappeared all right, and 
being recaptured, was replaced in the nest. 
Later in the season, on a secluded lake in one of the 
Hebrides, I observed a Dun-diver, or female of the Red- 
breasted Merganser ( Mergus Serrator), with her brood of 
young ducklings. On giving chase in the boat, we soon 
found that the young, although not above a fortnight old, 
had such extraordinary powers of swimming and diving, 
that it was almost impossible to capture them. The dis- 
tance they went under water, and the unexpected places in 
which they emerged, baffled ail our efforts for a consider- 
able time. At last one of the brood made for the shore, 
with the object of hiding among the grass and heather 
which fringed the margin of the lake. We pursued it as 
closely as we could, but when the little bird gained the 
shore, our boat was still about twenty yards off. Long 
drought had left a broad margin of small flat stones and 
mud between the water and the usual bank. I saw the 
little bird run up about a couple of yards from the water, 
and then suddenly disappear. Knowing what was likely 
to be enacted, I kept my eye fixed on the spot ; and when 
the boat was run upon the beach, I proceeded to find and 
pick up the chick. But on reaching the place of disappear- 
ance, no sign of the young Merganser was to be seen. The 
closest scrutiny, with the certain knowledge that it was 
there, failed to enable me to detect it. Proceeding cau- 
tiously forwards, I soon became convinced that I had al- 
ready overshot the mark ; and, on turning round, it was only 
to see the bird rise like an apparition from the stones, and 
dashing past the stranded boat, regain the lake, — where, 
having now recovered its wind, it instantly dived and dis- 
appeared. The tactical skill of the whole of this manoeuvre, 
and the success with which it was executed, were greeted 
with loud cheers from the whole party ; and our admiration 
was not diminished when we remembered that some two 
weeks before that time the little performer had been coiled 
up inside the shell of an egg, and that about a month be- 
fore it was apparently nothing but a mass of albumen and 
of fatty oils. 
The third case of animal instinct which I shall here men- 
tion was of a different but of an equally common kind. In 
walking along the side of a river with overhanging banks, 
I came suddenly on a common Wild Duck ( Anas Boschas), 
whose young were just out. Springing from under the 
bank, she fluttered out into the stream with loud cries and 
with all the struggles to escape of a helplessly wounded 
bird. To simulate the effects of suffering from disease, or 
from strong emotion, or from wounds upon the human 
frame, is a common necessity of the actor’s art, and it is not 
often really well done. The tricks of the theatre are seldom 
natural, and it is not without reason that “ theatrical ” has 
become a proverbial expression for false and artificial re- 
presentations of the realities of life. It was therefore with 
no small interest that on this, as on many other occasions, 
I watched the perfection of an art which Mrs. biddons might 
have envied. The labored and half convulsive flapping of 
the wings, the wriggling of the body, the straining of the 
neck, and the whole expression of painful and abortive 
effort, were really admirable. When her struggles had car- 
ried her a considerable distance, and she saw that they 
produced no effect in tempting us to follow, she made re- 
sounding flaps upon the surface of the water, to secure that 
attention to herself which it was the great object of the 
manoeuvre to attract. Then rising suddenly in the air, she 
made a great circle round us, and returning to the spot, re- 
newed her endeavors as before. It was not, however, ne- 
cessary ; for the separate instinct of the young in successful 
hiding effectually baffled all my attempts to discover them. 
Let us now look at the questions which these several ex- 
hibitions of animal instinct cannot fail to suggest ; and first 
let us take the case of the young Dipper. There was no 
possibility of imitation here. The rivulet beneath the nest, 
even if it had been visible to the nestlings, had been dry 
ever since they had been hatched. The river into which it 
ordinarily flowed was out of sight. The young Dippers 
never could have seen the parent birds either swimming or 
diving. This, therefore, is one of the thousand cases which 
have driven the “ experience” school of philosophy to take 
up new ground. The young Dipper here cannot possibly 
have had any experience, either through the process of 
incipient effort, or through the process of sight 
and imitation. Nature is full of similar cases. In 
face of them it is now no longer denied that in all such 
cases ‘‘innate ideas” do exist, and that “ pre-established 
harmonies” do prevail in Nature. These old doctrines, so 
long ridiculed and denied, have come to be admitted, and 
the new philosophy is satisfied with attempts to explain 
how these “ ideas ” came to be innate, and how these har- 
monies came to be pre-established. The explanation is, 
that though the efficiency of experience as the cause or 
source of instinct must be given up as regards the indi- 
vidual, we may keep it as regards the race to which the in- 
dividual belongs. The powers of swimming and diving 
and the impulse to use them for their appropriate purpose, 
were inaeed innate in the little Dipper of 1874. But then 
they were not innate in its remote progenitors. They were 
acquired by those progenitors through gradual effoit — the 
trying leading to success, and the success again leading to 
more trying — both 'ogether leading first to special faculty; 
I then to confirmed habit, and then, by hereditary transmis 
