The reproductive cycle and the development of Heliocidaris erythrogramma were investigated. The reproductive cycle was examined by regular, monthly samplings of urchins and routine histological techniques. Histochemical tests were employed to establish the phases of the reproductive cycle. Spawning and artificial fertilization were investigated in the laboratory, and the development of H. erythrogramma was followed from fertilization, through cleavage, blastulation, gastrulation, to development of the larva and metamorphosis into the juvenile urchin. A table of abnormal individuals was compiled, and representatives were sectioned in order to provide a better understanding of the processes involved in normal development
