A _Wellingtonia gigantea_, with its stupendous height and graceful form, with its bark and wood, and sap and pith, and cones and innumerable spikelets, seems wonderfully noble and vastly superior in the scale of creation to a spoonful of salt; yet every one of the tiny grains has, so far as we know, full as much sense and as much power of enjoyment as the stately tree. The mineral and the vegetable are, in fact, alike destitute of any qualities on which a comparison of dignity can properly be founded. The organic depends ultimately upon the inorganic for its nutriment. It is itself ultimately reduced to the inorganic. It does not, therefore, seem incredible that living organisms, simpler perhaps than any yet detected by the microscope, should be or should have been produced without generation proper by the mere combining of inorganic materials. This is the hypothesis of Spontaneous Generation, so called, or _abiogenesis_, unproved and extremely difficult of proof, but precisely filling that gap in the order and continuity of nature which is so puzzling without it. Practically it makes no difference to the theory of development whether the simple organisms from which that theory supposes the more complicated to be derived, originated at a single era or at several. The theory does not deny the perpetuation throughout vast ages of extremely simple organisms. To the general cohesion of the theory, therefore, it is unimportant whether we affiliate each of these living motes to a parent like itself, or to a combination of chemical substances previously without life. Considering the vast results attributed to the principle of _variability_, it has been thought strange that any organisms should through great cycles of time have escaped its operation, and transmitted their original simplicity to an endless succession of descendants. On the hypothesis of spontaneous generation working continuously this difficulty would disappear; simple organisms would be continually losing their simplicity by variation, but new organisms of equal simplicity would continually appear in the world, spontaneously generated.