Environment and Reproduction

Abstract

SEVERAL attempts have been made to show that spawning in the sea and in fresh waters, and also in terrestrial conditions, is regulated by temperature. Many examples could be quoted to demonstrate that the rule is for a species to spawn earlier and to develop more quickly in warm water; that, in other words, the period of spawning is early in tropical seas and conditions, and later to the north and south of the tropical belt, and that the period of growth is increased with lowering of temperature. The factors at work, however, are more deep-seated than they appear to be at first sight. That this is so is at once clear from two correlated considerations: (1) There is a period, sometimes a long period, of ripening with reference to which spawning is the culmination, and during which somatic changes and migratory results are produced; and (2) all the adults do not participate in the ripening and spawning.