ANIMAL LIFE. 5^3 



and would doubtless suffer extinction in other apparently more con- 

 genial regions. Such is evidenced by the fact that certain formerly 

 arctic forms have secured survival or at least a postponement of extinc- 

 tion in low latitudes by ascending mountain peaks or ranges, the as-, 

 sumption being that such forms were pushed southward during glacial 

 periods and that some instead of retreating with the glacier took advan- 

 tage of high latitudes to secure similar conditions. But while adapta- 

 tions 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 con- 

 ditions for supporting life are also very severe, especially where alti- 

 tudes 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 bounda- 

 ries 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 imder the conditions that have 

 been established with the community life. Eeturn 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 



VOL. LXUI. — 33. 



