It seems to me that there is much confusion of ideas in the general statement of the variability of species so often repeated lately. If species do not exist at all, as the supporters of the transmutation theory maintain, how can they vary, and if individuals alone exist, how can the differences which may be observed among them prove the variability of species? The fact seems to me to be that while species are based upon definite relations among individuals which differ in various ways among themselves, each individual, as a distinct being, has a definite course to run from the time of its first formation to the end of its existence, during which it never loses its identity nor changes its individuality, nor its relations to other individuals belonging to the same species, but preserves the categories of relationship which constitute specific or generic or family affinity, or any other kind or degree of affinity. To prove that species vary it should be proved that individuals born from common ancestors change the different categories of relationship which they bore primitively to one another. While all that has thus far been shown is, that there exists a considerable difference among individuals of one and the same species.