ABSTRACT
THE free-living or so-called pelagic organisms of the sea, that is, those neither attached to nor living within the bottom, encompass a vast assembly of animals and plants, and range from unicellular microscopic bacteria to those highly specialized giant aquatic mammals, the whales. In spite of this, the principles used in sampling them are relatively few; the majority are caught by nets or traps, some by hook and line, others by harpoon; the actual forms that the techniques take are, however, many and varied. For purely qualitative work, for example in studies of form and anatomy, it matters little how the animals are caught. The only criterion of success is that they are caught in adequate numbers and in a sufficiently undamaged condition for the particular problem in hand. It is when we wish to make quantitative investigations that difficulties arise in sampling these free-living forms.
