If we vividly picture to ourselves this “_unity of organic and inorganic nature_” this essential agreement of organisms and anorgana in matter, form, and force, and if we bear in mind that we are not able to establish any one fundamental distinction between these two groups of bodies (as was formerly generally assumed), then the question of spontaneous generation will lose a great deal of the difficulty which at first seems to surround it. Then the development of the first organism out of inorganic matter will appear a much more easily conceivable and intelligible process than has hitherto been the case, whilst an artificial absolute barrier between organic or animate, and inorganic or inanimate nature was maintained. In the question of _spontaneous generation, or archigony_, which we can now answer more definitely, it must be borne in mind that by this conception we understand generally the _non-parental generation of an organic individual_, the origin of an organism independent of a parental or producing organism. It is in this sense that on a former occasion (p. 183) I mentioned spontaneous generation (archigony) as opposed to parental generation or propagation (tocogony). In the latter case the organic individual arises by a greater or less portion of an already existing organism separating itself and growing independently. (Gen. Morph. ii. 32.) In spontaneous generation, which is often also called original generation (generatio spontanea, æquivoca, primaria etc.), we must first distinguish two essentially different kinds, namely, _autogeny_ and _plasmogeny_. By _autogeny_ we understand the origin of a most simple organic individual in an _inorganic formative fluid_, that is, in a fluid which contains the fundamental substances for the composition of the organism dissolved in simple and loose combinations (for example, carbonic acid, ammonia, binary salts, etc.). On the other hand, we call spontaneous generation _plasmogeny_ when the organism arises in an _organic formative fluid_, that is, in a fluid which contains those requisite fundamental substances dissolved in the form of complicated and fluid combinations of carbon (for example, albumen, fat, hydrate of carbon, etc.). (Gen. Morph. i. 174, ii. 33.)