M. Naudin admits the existence of a _protoplasma_ or _primordial blastema_, the origin of which he does not pretend to explain nor its entrance into action. Under the influence of the _organo-plastic_ or _evolutive force_ there were formed _proto-organisms_ of a very simple structure, asexual, and endowed with the power of producing by buds and with a great activity _meso-organisms_, similar to the first, though already more complicated. With each generation forms are multiplied, and become more pronounced, and nature rapidly passes on to the _adult state_. The beings in question were not, however, _species_. They were not complete beings, but merely a kind of _larvæ_, whose sole duty was to serve as transitions between the primitive blastema and the definite forms. Dispersed in different regions of the globe, they have carried everywhere the germs of future forms which _evolution_ had to produce from them. From the _creative_ character which distinguished it at first, the evolutive force exhausted by its very action, acquired a _preservative_ character. Forms are now _integrated_. They preserve, however, a residue of _plasticity_; they vary under the influence of certain conditions, and hence results the multitude of forms which the same species now presents. The proto- and meso-organisms contained in themselves, each according to its position in the order of evolution, the rudiments of kingdoms, branches, classes, orders, families, and genera. Points where they were fixed, became so many _centres of creation_. Moreover, they have not engendered simultaneously all the forms which they were capable of producing. There have been considerable intervals between the production of living beings, which explains why groups of the same order have not been contemporaneous. Organic types, even those least marked, have not passed into each other. The paths followed by the evolutive force have always been divergent. “Let us picture to ourselves,” says M. Naudin, “the meso-organism which has been the source of the mammalia; ever since its appearance, all the mammalian orders, including the human order, were fermenting in it. Before their appearance, they were virtually distinct, in the sense that the evolutive forces were already distributed, and the method of their effecting, each in its proper time, the production of these different orders, already defined. This is a similar phenomenon to that of the evolution of organs in a growing embryo, where we see springing from a common and uniform origin, parts at first similar, but which are impelled in a determinate direction each by its own particular _future_.”