Mr. Sorby on the Evolution of Hæmoglobin

IN the short notice in NATURE (vol. xiii. p. 257) of my paper on the Evolution of Hæmoglobin, in the Quarterly Microscopical Journal , it is said that my conclusions are mainly based on a small difference in the wave-length of the absorption-bands of the spectrum of the red blood of Planorbis . This is, however, a very small part of the question. The principal results are that hæmatin is first met with in the bile of many pulmoniferous molluscs in an abnormal state, quite unfit to serve the purposes of respiration, but easily changed into the normal, which could, and probably does in some cases, perform that function. Then in the blood of Planorbis we have a solution of a hæmoglobin, in which the hæmatin is combined with an albuminous constituent coagulating at the low temperature of 45° C., and finally we come to the normal hæmoglobin existing as red corpscules , containing an entirely different albuminous constituent, coagulated at about 65° C. In all these changes in the condition of the si me fundamental radical, the oxygen carrier becomes of more and more unstable character, and more fitted for the purposes of respiration, as we advance from lower to higher types, as though advantage had been taken of every improvement due to modified chemical or physical constitution.