Certain branches detached from the great ethnical stocks have already offered similar evidences. The Gipsies, Aryans mixed, perhaps, with Dravidians, have overrun the whole of Europe, and are now met with everywhere. As to the Jews, we know that they are really cosmopolitan, and that almost everywhere, in Prussia as in Algeria, their fecundity surpasses that of the local races. III. I do not mean by this that I consider the Aryan, or any races, capable of always becoming at once acclimatised in any given locality. On the contrary, there are regions which are fatal to man, to whatever group he may belong, and however well prepared he may seem to be to brave their influence. Such is the great estuary of the Gaboon, where the Negro himself cannot live. The general constitution of the inhabitants grows sensibly weaker; the reproductive organs appear to be particularly affected, and the number of women greatly surpasses that of the men. We know how dangerous the climate of this country is to the European, and it will be interesting to see whether the Paouins will in their turn yield to the deleterious influence of these coasts, which they are gradually approaching. We need not, moreover, go so far for examples. Who does not know the reputation of the Maremma, and the marshes of Corsica? At one time the swamps of the Dombe, and the mouth of the Charente, in France, were scarcely less dangerous. Even where the conditions are much less severe, acclimatisation almost always demands numerous and melancholy sacrifices, which some anthropologists have done wrong to overlook. The fact is but too natural. A race, which has settled under the influence of certain conditions of existence, cannot effect a change without undergoing modification, and hence suffering. This fact will be noticed in some detail in the chapter dedicated to the formation of these derived groups from the species. I can here only point out the general law. IV. Thus, every colonization of a distant country must be regarded in the first place as a conquest attempted by the immigrating race. Now, whether the battle has to be fought with man or with the conditions of life, the victory is only gained at the cost of human life. We must not, however, exaggerate the extent of inevitable losses, and deny the possibility of acclimatisation. We must put the problem clearly, and seek for experimental data, whence the solution may be naturally deduced. Every question of acclimatisation comprises two terms, which are, so to speak, the _components_ of the _resultant_ which we are seeking for or studying. These terms are _race_ and _conditions of life_. We already know the exact significance of the former of these two words, and we shall presently consider in some detail what we are to understand by the latter. At present we will take it as simply representing all the conditions of existence presented by a given place, and proceed to point out its influence in acclimatisation.