Page:Through the Brazilian Wilderness by Theodore Roosevelt (1925).djvu/145

 prey and those that are preyed on, concealing coloration has not been a survival factor; throughout the ages during which they have survived they have gradually lost whatever of concealing coloration they may once have had—if any—and have developed a coloration which under present conditions has no concealing and perhaps even has a revealing quality, and which in all probability never would have had a concealing value in any “environmental complex” in which the species as a whole lived during its ancestral development. Indeed, it seems astonishing, when one observes these big beasts—and big waders and other water-birds—in their native surroundings, to find how utterly non-harmful their often strikingly revealing coloration is. Evidently the various other survival factors, such as habit, and in many cases cover, etc., are of such overmastering importance that the coloration is generally of no consequence whatever, one way or the other, and is only very rarely a factor of any serious weight.

The junction of the São Lourenço and the Paraguay is a day’s journey above Corumbá. From Corumbá there is a regular service by shallow steamers to Cuyabá, at the head of one fork, and to São Luis de Cáceres, at the head of the other. The steamers are not powerful and the voyage to each little city takes a week. There are other forks that are navigable. Above Cuyabá and Cáceres launches go up-stream for several days’ journey, except during the dryest parts of the season. North of this marshy plain lies the highland, the Plan Alto, where the nights are cool and the climate healthy. But I wish emphatically to record my view that these marshy plains,