Page:Popular Science Monthly Volume 63.djvu/517

Rh and would doubtless suffer extinction in other apparently more congenial regions. Such is evidenced by the fact that certain formerly arctic forms have secured survival or at least a postponement of extinction in low latitudes by ascending mountain peaks or ranges, the assumption being that such forms were pushed southward during glacial periods and that some instead of retreating with the glacier took advantage of high latitudes to secure similar conditions. But while adaptations to the rigorous conditions of high latitudes must mean great hardihood, it also means small chance for progress in other lines and we do not look for progressive development in such situations. The Esquimaux and Laps will hardly produce Gladstones, Blaines, Leo XIII.'s, Bismarcks or Grants. But while extreme cold is unfavorable to life, extreme heat is equally so, and the limits in this direction arc perhaps even more strictly marked.

Nevertheless, we find aquatic animals that have adapted themselves to life in hot springs, numerous forms living in water of 100° F., while some forms occurring in hot springs of the famous Yellowstone region exist in temperatures which, except to those especially adapted, would be destructive. On the barren slopes and crests of mountains the conditions for supporting life are also very severe, especially where altitudes are such as to leave all forest growth below or to reach into the regions of perpetual snow and ice. Still such inhospitable quarters are sought out by many animals and various small mammals, many birds and insects may be found keeping up the struggle against the boundaries to life's outskirts.

Another most interesting phase of adaptation is to be noted in the community life exhibited by ants, bees, termites and some other groups. The community habit has resulted in the development of various castes, some of which have assumed the full duty of reproduction, others fitted only for the labors or defense of the colony. In some cases slavery follows this division of labor, the members of other colonies or other species being kept in captivity and utilized in carrying on the duties of the colony except of course that of reproduction. In some species we are assured this has gone so far and the slave-making species has become so dependent on the slaves that without them they will die of starvation. Community life then is an extreme specialization offering many advantages, but at the same time entailing certain limitations, cutting off the individual from any possibility of independent existence and the colony from survival, except under the conditions that have been established with the community life. Return to primitive isolated life is manifestly impossible.

These constitute some of the most striking by-paths into which life forms have been diverted either from choice or necessity, but barely a