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VICTOR L. LOOSANOFF A N D HARRY C. DAVIS
responsible for these variations. However, by maintaining the cultures
at a constant temperature of 24°C and providing the larvae with good
food, such as Isochrysis galbana, we consistently bring cultures of
M . mercenaria t o the beginning of setting 12 days after fertilization.
In experiments designed to determine temperature limits for
development of eggs of C. virginicu it was found that at 17.5"C as
many as 97% of the eggs may develop to normal straight-hinge stage.