258 
H. SEEBOHM-NESTS AND EGGS OE BIRDS. 
solely rely for the protection of their eggs on their protective 
colouring. On the edge of the sand, where the sea washes up, 
there are colonies both of the arctic and the common tern; the eggs 
of these birds are darker than those of the sandwich-tern, and are 
evidently so coloured that when lying on the delicate seaweed they 
may be almost as inconspicuous as the sea-weed itself. 
On another island of the same group a very different style of 
nest-building is met with. This island is covered with turf, and a 
colony of puffins breed at the end of the rabbit-burrows which 
everywhere abound. The eggs are slightly spotted. You can see 
the spots when the egg is washed and clean. It is probable that 
in past ages the puffin laid its eggs in an open nest, and that then 
they were distinctly spotted; now that it adopts a rabbit-burrow, 
where no light can penetrate, the colouring-matter has been gradu¬ 
ally lost, and, unless the bird becomes extinct, they will eventually 
become as white as the eggs of other birds whose habit it is to 
breed in holes. It is difficult to say why the colour should be lost 
in cases of this kind where no protective selection can take place; 
but it seems to be a law in nature that any organ, which is not 
necessary for the use of an animal, becomes in consequence of 
disuse more and more rudimentary, until it almost ceases to be con¬ 
sidered an organ at all, and that the converse proposition is equally 
true. In other words, that organs increase and strengthen by use 
and decrease by absence of use. Take as an example a bird very 
nearly allied to the guillemot—the great auk. It is only about 
forty years since the last great auk was seen, and yet specimens of 
this bird are now worth £500 each, and its eggs, more or less 
damaged, were recently sold by auction in London for 100 guineas 
and 105 guineas each. It was completely unable to fly; it had a 
wing, but it was only four or five inches long, and in consequence 
of not having been used for many generations, it became of so rudi¬ 
mentary a character that it was practically useless. The case of 
the great auk may be accepted as an illustration, not certainly of 
the survival of the fittest, but of the extinction of the most unfit. 
We must not dwell longer on the interesting Tern Islands, but 
will imagine ourselves transported to the wilds of the Siberian 
tundra, beyond the limits of forest-growth, into a district of mosses, 
bogs, and swamps, of rivers and lakes, everything except trees, 
there not being a single tree within a thousand miles. You may 
think that places such as this, covered during eight months of the 
year six feet deep in snow, could hardly be good for birds-nesting ; 
but I must inform you that what is called in Siberia a tundra, and 
in England a moor, is one of the great bird-nurseries of the world. 
Here you may find hundreds of birds which visit the coasts of 
England during the winter: sandpipers, different kinds of geese, 
ducks, swans, and many others, all content enough to spend the 
winter months in the south, but invariably retreating in the spring for 
breeding purposes to the wild Arctic regions in the north of Europe. 
The summer in northern Siberia is very short; for three months 
the sun never sets; there are twenty-four hours of sunshine every 
