1. INTRODUCTION
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It appears appropriate a t this point to quote from Laing (1937)
who has stated :
The objects sought by any animal are different at successive periods of
existence-food at one time, shelter, a mate, or a medium for oviposition
in others. Which of these objects should be sought at any particular time
depends, clearly, upon the internal conditions of the animal, for example, its
state of hunger or the ripeness of its germ cells. In addition, the immediate
behavior of the animal is directly affected by external factors.
Thus, in dealing with marine symbioses, certain factors contributed
by the marine environment obviously must differ from factors contributed by a terrestrial or freshwater environment. It is these different
" external factors ", along with obvious differences that exist between
distinct taxonomic categories of hosts and symbionts, which render
marine symbiology unique. As this review serves to point out, a t this
time very little is yet known about " external factors " that influence
symbioses in the marine environment, although such factors
undoubtedly exist.