lay on the ground.

The method of the work explains these differences. The concrete of our
buildings is obtained by the simultaneous manipulation of gravel and
mortar. In the same way, the Spider mixes the cement of the silk with
the grains of sand; the spinnerets never cease working, while the legs
fling under the adhesive spray the solid materials collected in the
immediate neighbourhood. The operation would be impossible if, after
cementing each grain of sand, it were necessary to stop the work of the
spinnerets and go to a distance to fetch further stony elements. Those
materials have to be right under her legs; otherwise the Spider does
without and continues her work just the same.

In my cages, the sand is too far off. To obtain it, the Spider would
have to leave the top of the dome, where the nest is being built on its
trellis-work support; she would have to come down some nine inches. The
worker refuses to take this trouble, which, if repeated in the case of
each grain, would make the action of the spinnerets too irksome. She
also refuses to do so when, for reasons which I have not fathomed, the
site chosen is some way up in the tuft of rosemary. But, when the nest
touches the ground, the clay rampart is never missing.

Are we to see in this fact proof of an instinct capable of modification,
either making for decadence and gradually neglecting what was the
ancestors' safeguard, or making for progress and advancing, hesitatingly,
towards perfection in the mason's art? No inference is permissible in
either direction. The Labyrinth Spider has simply taught us that
instinct possesses resources which are employed or left latent according
to the conditions of the moment. Place sand under her legs and the
spinstress will knead concrete; refuse her that sand, or put it out of
her reach, and the Spider will remain a simple silk-worker, always ready,
however, to turn mason under favourable conditions. The aggregate of
things that come within the observer's scope proves that it were mad to
expect from her any further innovations, such as would utterly change her
methods of manufacture and cause her, for instance, to abandon her cabin,
with its two entrance-halls and its star-like tabernacle, in favour of
the Banded Epeira's pear-shaped gourd.

CHAPTER XVI: THE CLOTHO SPIDER

She is named Durand's Clotho (_Clotho Durandi_, LATR.), in memory of him
who first called attention to this particular Spider.