• 1
     The displacement method of weighing living aquatic organisms has been extended.
  • 2
     The present paper deals chiefly with the densities and water-content of the ovaries, ova and embryos of decapod Crustacea.
  • 3
     A rapid method of estimating fats without previous drying is described.
  • 4
     A rapid method of weighing living tissues whose density is known is described.
  • 5
     A quantitative examination of the sponge Ficulina ficus and the density of protoplasm is given. The density of protoplasm was found to be 1–0565 at 15o C. This gives a sinking factor of 1026.
  • 6
     The density and water-content of the jelly-fish, Aurelia aurita, is given. The percentage of water is 95-56. This agrees closely with the figure given by Hyman, 96-0%. The figure given by Gortner, 99-8%, is clearly impossible.
  • 7
     The density and -water-content of Pleurobrachia pileus are given. The water-content is 94-73% and the sinking factor 1000-2.
  • 8
     The density and water-content of the ovaries, ova and embryos of Palinurus vulgaris, Homarus vulgaris, Carcinus msenas, Cancer pagurus and Maia squinado are given.
  • 9
     In decapod Crustacea the density of the resting ovary approximates to that of protoplasm and greatly increases as the ova develop. The early embryos are far too dense to swim even by limbs, if they were present.
  • 10
     The densities of the ovary and ova of four species of Echinodermata have been found. Unlike the decapod Crustacea, as the ova develop there is a decrease in density, giving an early embryo of a sufficiently low density to be supported readily by cilia.
  • 11
     The density and water-content, also fat and nitrogen, of the ovaries and ova of Scyllium canicula have been found.
  • 12
     The density and water-content of the muscle of Homarus, Acanthias, a Ray, the Cod and the Saithe have been found.
  • 13
     The density of the embryos of such copepods as Cyclops strenuus and Calanu8 finmarchicus is discussed.