her on the
same level, have a very pleasing general effect. No pilgrim returning
from Santiago de Compostella ever slung handsomer tippet from his
shoulders.

But only too often the caddis worm dashes ahead, regardless of
proportion. The big is joined to the small, the exaggerated suddenly
stands out, to the great detriment of order. Side by side with tiny
Planorbes, each at most the size of a lentil, others are fixed as large
as one's fingernail; and these cannot possibly be fitted in correctly.
They overlap the regular parts and spoil their finish.

To crown the disorder, the caddis worm adds to the flat spirals any dead
shell that comes handy, without distinction of species, provided it be
not excessively large. I notice, in its collection of bric-a-brac, the
Physa, the Paludina, the Limnaea, the Amber snail [all pond snails] and
even the Pisidium [a bivalve], that little twin-valved casket.

Land shells, swept into the ditches by the rains after the inmate's
death, are accepted quite as readily. In the work made of the Mollusk's
cast-off clothing, I find encrusted the spindle shell of the Clausilium,
the key shell of the pupa, the spiral of the smaller Helix, the yawning
volute of the Vitrina, or glass snail, the turret shell of the Bulimus
[all land snails], denizens all of the fields. In short, the caddis worm
builds with more or less everything that comes from the plant or
the dead mollusk. Among the diversified refuse of the pond, the only
materials rejected are those of a gravelly nature. Stone and pebble are
excluded from the building with a care that is very rarely absent. This
is a question of hydrostatics to which we will return presently. For the
moment, let us try to follow the construction of the scabbard.

In a tumbler small enough to allow of easy and precise observation, I
install three or four caddis worms, extracted this moment from their
sheaths with every possible precaution. After a number of attempts which
have at last shown me the right road, I place at their disposal two
kinds of materials, possessing opposite qualities; the supple and the
firm, the soft and the hard. On the one hand, we have a live aquatic
plant, such as watercress, for instance, or ombrelle d'eau, having
at its base a tufty bunch of fine white roots about as thick as a
horsehair. In these soft tresses, the caddis worm, which observes a
vegetarian diet, will find at one and the same time the wherewithal to
build and eat.