Life in the allobiosphere.

G. Evelyn Hutchinson, whose ideas have stimulated so much of modern ecology, coined the term allobiosphere to denote regions where photosynthesis is precluded by environmental extremes of darkness, drought, heat or cold, and where life depends for sustenance on imported materials. The occupants of the allobiosphere arc living on the edge; to appreciate their circumstances is to broaden our perspective of the mainstream. Recent and continuing studies on two contrasting components of the biosphere, the ocean depths and volcanic islands, are independently giving sharper outline to what was at best a hazy sketch of the allobiosphere. My aim here is to juxtapose these radically different extremes.