of a filbert, then carried to the nest. When finished the structure is
shaped outwardly like a baker's oven, only with a deeper and narrower
entrance. It is always placed very conspicuously, and with the
entrance facing a building, if one be near, or if at a roadside it
looks towards the road; the reason for this being, no doubt, that the
bird keeps a continuous eye on the movements of people near it while
building, and so leaves the nest opened and unfinished on that side
until the last, and then the entrance is necessarily formed. When the
structure has assumed the globular form with only a narrow opening,
the wall on one side is curved inwards, reaching from the floor to the
dome, and at the inner extremity an aperture is left to admit the bird
to the interior or second chamber, in which the eggs are laid. A man's
hand fits easily into the first or entrance chamber, but cannot be
twisted about so as to reach the eggs in the interior cavity, the
entrance being so small and high up. The interior is lined with dry
soft grass, and five white pear-shaped eggs are laid. The oven is a
foot or more in diameter, and is sometimes very massive, weighing
eight or nine pounds, and so strong that, unless loosened by the
swaying of the branch, it often remains unharmed for two or three
years. A new oven is built every year, and I have more than once seen
a second oven built on the top of the first, when this has been placed
very advantageously, as on a projection and against a wall."[102]

[102] P. L. Sclater and W. H. Hudson, _Argentine
Ornithology_, 1888, vol. i. pp. 168, 169. See also
Burmeister, "Ueber die Eier und Nester einiger
brasilianischen Voegel," _Cabani's Journal fuer Ornith._,
1853, pp. 161-177.

_Masons working in association._--Ants have already furnished us with
numerous proofs of their intelligence and their prodigious industry.
So remote from Man from the anatomical point of view, they are of all
animals those whose psychic faculties bring them nearest to him.
Sociable like him, they have undergone an evolution parallel to his
which has placed them at the head of Insects in the same way as he has
become superior to all other Mammals. The brain in Ants as in Man has
undergone a disproportionate development. Like Man, they possess a
language which enables them to combine their efforts, and there is no
human industry in which these insects have not arrived at a high
degree of pe