Experiments on the Interchange of Oxygen and Carbon Dioxide between the Skin of Lepidosiren and the surrounding Water, and the probable Emission of Oxygen by the Male Symbranchus



  • 1The object of the experiments recorded was to discover how much of the decrease in dissolved oxygen in water surrounding a specimen of Lepi-dosiren is due to the absorption by mucus etc. of iodine liberated by the Winkler reaction, and how much to the absorption of dissolved oxygen from the water either by the mucus or by the fish itself.
  • 2It was found that the excreted mucus did not absorb oxygen directly, that it was not precipitated by acetic acid or ammonium sulphate, that it was slightly coagulated by absolute alcohol, and that it reduced Fehling's solution after hydrolysis and standing three days.
  • 3The absorption of iodine by the mucus was definitely proved and measured.
  • 4The absorption of oxygen by the skin of Lepidosiren was found to be considerable in water saturated with the gas, and to decrease with the degree of concentration.
  • 5The pH of thewater of the Metropolitan Water Board supply containing mucus from Lepidosiren was found to be 7.5, and in its original condition perhaps a little nearer to 7–6.
  • 6The emission of CO2 from the skin of the fish was tested by titration with sodium carbonate, phenolphthalein being used as indicator, and from 4.05 to 8.12 C.C. were found to be given off in one hour.
  • 7It is pointed out that the emission of oxygen by the pelvic filaments is not a process entirely unrelated to the ordinary diffusion of oxygen in respiration, but a specialization of a general process—namely, the emission of oxygen from the skin when the concentration of that gas is lower in the surrounding water than in the blood and lymph within the skin.
  • 8A sex-limited character in Symbrandus is described, consisting of the red ground-colour of the skin of the male, in contrast with the yellow in the female. This red colour seems to be due to greater vascularity of the skin in the male, and it is suggested that this incroased supply of blood enables the whole of the skin to emit sufficient oxygen for the respiration of the eggs and larvt-e in the nest-burrow, and thus perform the same function as the pelvic; filaments of the male Lepidosiren.