When built upon a horizontal base of sufficient extent, it is a dome with a central neck, funnelled like the mouth of an urn.

But when the foundation is reduced to a mere point, as on the twig of a shrub, the nest becomes a spherical capsule, always, of course, surmounted by a neck.

It is then a miniature specimen of exotic pottery, a paunchy alcarraza.

Its thickens is very slight, less than that of a sheet of paper; it crushes under the least effort of the fingers.

The outside is not quite even.