Many German biologists find themselves compelled, by the impossibility of explaining vital activities in terms of chemistry or physics, to associate protoplasm with some kind of psychical activity.[124] Individuality, at least, implies an ultra-material principle, and it asserts itself at the very base of the animal creation. An amœba is the simplest of living beings. Formerly called the 'Proteus animalcule,' it is 'everything in turn, and nothing long.' It can be round or radiated, spherical or lenticular, as momentary convenience prescribes. Organs it has none, its limbs are conspicuous by absence, it is 'sans everything' that belongs to the ordinary outfit of an animated creature. Yet such-like nucleated globules of protoplasm have flourished exuberantly during countless ages. Adaptability insured survival. An amœba is at home in almost any environment. What it has not ready-made, it can supply at a moment's notice. Out of any part of its substance it can improvise feelers and tentacles for the capture of its prey, as well as a stomach for its digestion, and it thus effectively goes through the full round of animal economy. Some varieties, too, are noted builders. Those called Foraminifera have the faculty of secreting carbonate of lime from sea-water, and construct with it fairy dwellings, perforated in all directions to allow of the protrusion of exploratory filaments. Fossil chambered shells of this type are extraordinarily abundant. Their dense conglomeration in the chalk elicited Buffon's exclamation that 'the very dust had been alive!'[125] The _calcaire grossier_ of which Paris is built consists mainly of them, and to this day, in oceanic depths, the materials of future capitals are in course of preparation by the monumental industry of these unpretending creatures.