After a very long and exhaustive survey of the plants and animals of his own locality, and of all that the power and favor of Alexander the Great enabled him to inspect, this is the result to which Aristotle, the prince of ancient Greek naturalists, came. In the eighth book of his "History of Animals," when speaking of the chain of living things, he says: "Nature passes so gradually from inanimate to animate things, that from their continuity the boundary between them is indistinct. The race of plants succeeds immediately that of inanimate objects, and these differ from each other in the proportion of life in which they participate; for, compared with minerals, plants appear to possess life, though when compared with animals they appear inanimate. The change from plants to animals is gradual; a person might question to which of these classes some marine objects belong." Aristotle referred the primitive organisms to spontaneous generation.
In the Museum of Alexandria the views of Aristotle were greatly expanded. There it was discovered that animated Nature presents something more than a mere connection; that each link of Aristotle's chain, if such a phraseology must be continued, was the descendant of its predecessor, the progenitor of its successor. The idea now lost its mechanical aspect and assumed a physiological one.
We remark an important extension of this view after the conquest of Alexandria by the Arabians. If we compare the order of affiliation in successive points, it obviously presents a new fact—progress; and not progress only, but progress from the imperfect to the more perfect. This view included lifeless as well as living Nature. A practical application of it arose, to which the designation Alchemy was given. There is an unceasing progression, in which all things take part, to a better and nobler state. In this slow development Nature has no need to hasten; she has eternity to work in. Thus, in the mineral world, base and unworthy metals, such as lead and tin, are slowly on their way to perfection. They reach their goal on turning into gold. It is, then, for us to ascertain the favoring conditions, and, by imitating or increasing them, to hasten on the work.
The literature of those ages is pervaded with the idea of the mutability of everything—a proneness of all living beings to suffer transmutation, with changes in the environment, or in the physical conditions to which they are exposed; and thus arises a slow but continuous procession, in the unceasing lapse of time, to the beautiful and good. We meet with this in both the serious philosophical works of the Mohammedans, and in their lighter compositions of romance. They wrote books on the production of animals both by generation and putrefaction. They thought that in the germ there exists a latent force tending to evolve it. Ibn Roschd says: "There are, as respects the origin of living beings, two opposite theories. Some explain their existence by development, others by creation. The latter is the opinion of the Christians, as well as of our Motacallemin." Abubacer
