V. The reproductive cycle of the three-spined stickleback, Gasterosteus aculeatus , Linn

Abstract

A study has been made of the cyclical changes which occur annually in the reproductive organs of a fish living in a temperate climate. The fish chosen has marked seasonal secondary sexual characters in the male, and the relation between the development of these and the changes in the testis has been investigated in detail. An experimental examination, suggested by these studies, has been made of the possible influences of physical and biological changes in the environment on the reproductive cycle. The migration of the fish which occurs in connection with reproduction was examined to ascertain whether it bears a relation to the reproductive cycle.