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Summary.

  • 1
     In natural populations parthenogenetic egg production in Daphnia magna Straus is directly related to size.
  • 2
     Previous workers have shown that the number of parthenogenetic eggs produced during the life of a female increases in the early broods and decreases in later broods.
  • 3
     Egg production and size are positively correlated in the first adult instar, both under constant conditions and with varying food.
  • 4
     The size of the young liberated varies with maternal age, the third brood consisting of young of a larger average size than earlier or later broods.
  • 5
     The initial size of the young liberated influences the instar in which maturity is reached.
  • 6
     The probable effects of maternal age on growth, maturation and longevity of the young are discussed.