surface was falling through those ranges of temperature at which the higher organic compounds are unstable.' But the 'reason why' is to seek. A sterilized solution is precisely one which has cooled from a high thermal grade; a baked brick is similarly circumstanced. Why should the appearance of life in primeval times have been favoured by a state of things fatal to it here and now? The essence of the biological crux resides in 'protoplasm.' The word was coined by Von Mohl in 1846, with the object of emphasizing the importance of the substance it signified, which indeed forms the bulk of every organism, animal and vegetable, man, mushroom, and amœba. Huxley rightly termed it 'the physical basis of life,' adding, however, the infelicitous conjecture that its production might have been one of the lucky hits of nature. It would have been a hit of incalculable moment, but of incalculable improbability. 'Odds beyond arithmetic' were against that particular throw coming out of the Lucretian dice-box. The 'primal slime' (to use Oken's phrase) is composed of oxygen, nitrogen, hydrogen, and carbon, with minute percentages of phosphates and other salts. But these constituents are put together in a highly artificial manner. Eight or nine hundred elementary atoms, in fact, go to the making of one molecule of protoplasm, forming a structure of extreme complexity, most delicately balanced and eminently unstable. It results, accordingly, from the employment of specially directed forces, and stores, for the benefit of the producing organism, the energy expended in its construction. Left to itself, it promptly goes to pieces, and yields back its component particles to their native inorganic sphere. The laws there ruling are in truth adverse to the existence of protoplasm; abandoned to their unmitigated action, it perishes. We should then as reasonably suppose that in the geological past rivers flowed uphill as that inorganic nature stumbled blindly upon this wonderful postulate and product of life.