which find their way outwards to a position of equiôÙlibôÙrium in the surface-layer; and in both cases, the mutual capillary attractions between the particles, confined to the boundary-layer but enjoying a certain measure of freedom therein, tends to the orderly arrangement of the particles one with another, and even to the appearance of a regular ãpatternã as the result of this arrangement.
The ãpicking upã by the protoplasmic organism of a solid particle with which ãto build its houseã (for it is hard to avoid this customary use of anthropomorphic figures of speech, misleading though they be), is a physical phenomenon