In the same manner precisely there was a prior period when no such substance as a crystal existed, the conditions requisite for the peculiar combination of molecular atoms to result in the formation of a crystal having been absent. When the world had undergone sufficient evolutionary development there came a time when such atmospheric and other conditions were present as to permit of a modification of the then existing substances and properties, which resulted in the formation of the crystal; and, precisely in the same manner, and for the same reason, a further and later modification resulted in the formation of Protoplasm, which is the earliest form of animal life. This little substance gradually differentiated into two distinct parts, by a nucleus being formed in the centre of the protoplasmic mass, and became possessed with a peculiar power of locomotion, which caused a still greater difference to exist between itself and its ancestral stock. This power of locomotion, again, is but a modification of that life-power of which we have spoken, and forms a stepping-stone between the molecular action of mineral substances and the mental wonders of the human being. The crystal, in common with all other bodies in the mineral kingdom, always possessed this power of locomotion to a limited extent; every one of the individual atoms which make up the whole substance has always had the power of locomotion, for they all attract and repel each other and effect cohesions by their mutual attraction. This locomotive power underwent such a modification when cell-life (Protozoa) was manifested that not only were the constituent molecular atoms individually possessed of this power, as before, but the whole mass of the cell became endowed with the same property, just as a whole continent of free people who have been in the habit of defending themselves singly against their enemies sometimes combine and co-operate with each other in the form of a republic, the function of the individual being assumed by the body as a whole. The little cellular organisms, which are called Amœbæ, possess this extended power of locomotion, and may be seen constantly moving about in the endeavour to locate themselves in the brightest part of their dwelling place, frequently a little pond. They are attracted by light, which clearly proves that they possess a degree of sensory perception, although special sense-organs are of course wanting, the whole mass of the body being nothing more than a single cell composed of protoplasm and nucleus. These little cellular organisms soon unite with each other, forming small bodies composed of several cells in a state of cohesion (Synamœbæ), and on the surface of these multicellular organisms are shortly afterwards thrown out minute threads or ciliae, the first attempt at separation of sense-organs from the surface of the body. In these tiny Protozoa, those organisms which consist of one single cell only, the Amœbæ, as well as those