The seas of the earth are vast. But, paradoxically, in that vastness there are few chance encounters. The waters, like the land, are covered by a network of paths and highways. Every species of life in the oceans has its route, and there are routes for every season. Nothing in this elaborate web of traffic has been left to chance. It has all been worked out in detail. It is all rigorously control­led by biological factors. And it works out greatly to the advantage of seafar­ers like ourselves whose mission it is to observe, and try to understand, the creatures who inhabit the seas.