In both these doctrines of a priori science Descartes has not been subverted, but, if anything, corroborated by the results of experimental physics; for the so-called atoms of chemical theory already presuppose, from the Cartesian point of view, certain aggregations of the primitive particles of matter.
The "crested" or "cock's comb" barytes occurs as rounded aggregations of thin lamellar crystals.
An example of the latter occurs in Singapore where the vicious red spinning-ant (Oecophylla smaragdina) is mimicked by the larva of a Noctuid moth and by spiders belonging to two distinct families, namely, Saltiicus plataleoides (Salticidae) and Amyciaea forticeps (Thomisidae), there being no reason to suppose that either the moth larva or the spiders are protected forms. Mimetic aggregations of species similar to those mentioned above have been found in other countries; but the instances cited are sufficient to show how widespread are the influences of mimicry and how profoundly it has modified the insect fauna of various parts of the world.
Such aggregations of hyphae frequently become knotted up into dense masses of interwoven and closely packed hyphae, varying in size from that of a pin's head or a pea (Peziza, Coprinus) to that of a man's fist or head, and weighing io to 25 lb or more (Polyporus Mylittae, P. tumulosus, Lentinus Woermanni, P. Sapurema, &c.).
These aggregations or colonies, as they are termed, may attached to muddy surfaces by rhizoids; Caulerpa, on the other, assume the form of a plate, a ring, a solid sphere, a hollow sphere, presents a remarkable instance of the way in which much the same a perforate sphere, a closed net, or a simple or branched filament.