s
the substance I mean--by which they fasten themselves to shells, or to
stones, roots, and other things.

[Illustration: ZEBRA MUSSEL.--_b._ BYSSUS.]

There flies one of those pretty little birds, the long-tailed
titmouse; it is common enough, certainly, but I never fail to notice
several upon the hedges and poplar trees of the "Duke's drive." There
are several members of the titmouse family found in Great Britain;
let me count them. First we have the great tit, then the little
blue-tit, the long-tailed tit, the cole tit, the marsh, the crested
and the bearded tit. How many does that make? Seven; but the crested
tit is very uncommon, and the bearded tit does not occur in
Shropshire. The other five are quite common and we shall, I dare say,
be able to see all in the course of to-day's walk. The long-tailed
tit, so called on account of the great length of the tail feathers, is
a very active, lively little bird. Indeed, activity and liveliness
belong to all the tit family. See how the little fellow flits from
branch to branch, seldom remaining long on one spot. It is a very
small bird, almost the smallest British bird we have; of course I am
thinking of the tit's body and not taking into account its tail. The
skin is remarkably tender, and thin as tissue paper. Like all the
titmice, the long-tailed tit feeds on insects and their larvae. I do
not remember to have heard or seen this species tapping the bark of a
tree with its beak, as the great and the blue tit are frequently in
the habit of doing, but most probably they do the same. "What do they
tap for, papa?" asked May. I suppose for the purpose of frightening
the tiny insects, which lurk under the bark, from their hiding places,
when they quickly snap them up with their sharply-pointed bills and
devour them. "Is not this the tit which the people about here call a
bottle tit, and which makes a very beautiful nest?" asked Willy. Yes,
the nest is indeed a very pretty object, and one that you would never,
I think, confuse with the nest of any other bird. The outside is
formed of that white-coloured lichen, so pretty and so common, and
moss, and if you were to put your finger, May, into the inside, which
is full of the softest feathers, you would say it was as nice as your
own muff. The nest is oval, with a hole at the side. I believe that
sometimes two holes exist, but I have never seen two in a nest. The
eggs are very small, and are white with a few lilac spots. As many