Hæmoglobin in Mollusca

Abstract

SIR RAY LANKESTER will find some interesting experiments on the usefulness of hæmoglobin to Planorbis and Chironomus larvæ in a paper by Leitch in the Journal of Physiology (vol. 1., 1916, p. 370), in which the author indicates that its respiratory value comes into play only when the oxygen pressure is quite low. This does not, of course, solve the problem as to why there should be various closely allied mollusca (Limnæa) living side by side with Planorbis, and with apparently equal success, which have no hæmoglobin beyond a trace in the muscles of their lingual apparatus. The possession of a considerable quantity of hæmoglobin seems to be a generic character, since it is present in all the species of Planorbis, which differ a good deal among themselves in their habits and in their capacity to live in clean and dirty water, and absent in all sorts of Limnæa. Sir Ray Lankester seems to have forgotten what he taught me in his elementary class twenty-six years ago: that hæmoglobin has come to have secondary (decorative) uses in man; but he will perhaps be as loath to admit an æsthetic sense in snails and their companions as he has been to accept the selective intelligence of Earland's foraminifera in building their tests. But the albino form of Planorbis corneus found by Mr. W. T. Webster near Barnet, in which the colour of the hæmoglobin is not obscured by black pigment, is certainly a gorgeous spectacle.