Page:Popular Science Monthly Volume 56.djvu/529



HE experiments which have been intentionally or accidentally made in transplanting organic species from the countries in which they have been developed to others of diverse soil, climate, and inhabitants are always of much interest to the naturalist—each of them affords indications of some value as to the relations of species to what we term "environment." In almost all instances we find that the transplanted forms undergo changes in consequence of the alteration of their circumstances. It is true that certain of our domesticated animals, such as the horse, the dog, and most cattle, follow men from the Arctic to the Antarctic Circle, and that sundry insect pests appear to demand nothing of Nature save the presence of man; yet, as a whole, the creatures we have turned to use, both plant and animal alike, have shown themselves incapable of accommodating themselves to conditions of temperature differing much from those in which they were developed. With hardly an exception, species or varieties which have been developed in the tropics perish when called on to withstand the winter of higher latitudes. Few, indeed, do well when taken to stations where the heat or the humidity differs greatly from that to which they are accustomed.

The intolerance of organisms to climatal changes is nowhere more evident than in the varieties, or species, as we would term them, of mankind. It is a well-attested fact that none of the tropical races has ever of its own instance colonized in the temperate zones. It is also clear that none of the northern peoples