The evolution theory . ^ in the transference of the free larvalstages to embryonic development the greatest possible condensationand abbreviation of the stages must have been striven for, whichcould only come about by a continual nuitual adaptation of theembryonic parts to one another, involving the suppression of every-. Fia. 114. Zonea-larva of a Crab,after R. Hertwig. J-F, tlie alreadyfunctional anterior appendages —antennae, mandibles,and swimming-legs, VI-XIII, ludiments of theposterior appendages of the eephalo-thorax {Cph\ Abd, the abdomen. 172 THE EVOLUTION THEORY thing superfluous. Ot
The evolution theory . ^ in the transference of the free larvalstages to embryonic development the greatest possible condensationand abbreviation of the stages must have been striven for, whichcould only come about by a continual nuitual adaptation of theembryonic parts to one another, involving the suppression of every-. Fia. 114. Zonea-larva of a Crab,after R. Hertwig. J-F, tlie alreadyfunctional anterior appendages —antennae, mandibles,and swimming-legs, VI-XIII, ludiments of theposterior appendages of the eephalo-thorax {Cph\ Abd, the abdomen. 172 THE EVOLUTION THEORY thing superfluous. Otherwise the transference of the free stages tothe embryogenesis would have brought no advantage, but rathera most prejudicial protracting of the development. We must not, therefore, expect to find the stages of thephylogen}^ occurring unaltered in every ontogeny in the way we havefound the nauplius, Zosea, or Mysis stages in the larval development ofthe Decapods. I have noticed already that in the water-fleas(Daphnidae) and other Crustaceans without metamorphosis thenauplius stage is still passed through, but within the egg, and as anembryonic stage, and this is quite true, but nevertheless it wouldhardly do to liberate a nauplius like this from its shell and place it inthe water, for the influence of the water
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Keywords: ., bookauthorthomsonj, bookcentury1900, bookdecade1900, bookyear1904
