MARCH 4, 1933 NATURE

invertebrates possess red corpuscles. So far, Letters to the Editor we have only had the opportunity of studying the respiratory from two such species. It is [The Editor does not hold himself responsible for noteworthy that in both cases low sedimentation opinions expressed by his correspondents. Neither constants were found. can he undertake to return, nor to correspond with The constancy of the molecular weights of the the writers of, rejected manuscripts intended for this respiratory blood proteins within various animal or any other part of NATURE. No notice is taken groups becomes still more puzzling when the following of anonymous communications.] facts are taken into consideration. The erythro• Molecular Weights of the Blood Pigments of the cruorin and the chlorocruorin of the polychoote Invertebrates worms, the of Planorbis and the hoomocyanin of Calocharis, the erythrocruorin of the BY means of the ultra-centrifugal method, it has polychoote worms and the hoomocyanin of Sepia and recently been shown that the red blood pigment of probably the erythrocruorin of Daphnia and the the is not identical with the hoomoglobin of hoomocyanin of Eupagurus have identical sedimenta• the vertebrates as was previously assumed, but is a tion constants and therefore probably identical more allied to chlorocruorin and hoomocyanin molecular weights. The measurement of the absorp• with regard to molecular weight'. It was suggested tion of light in the visible part of the spectrum for that a comparative study of the properties of the the blood proteins of the gastropods has further respiratory proteins throughout the animal kingdom shown that the hoomocyanins of Helix, Paludina and might bring to light interesting relationships between Littorina, which have the same molecular weight, the various groups of animals. Such an investigation nevertheless are distinctly different with regard to has now been started, and although so far only some the chemical constitution of the active group of the forty species have been studied, a number of molecule. A detailed and systematic investigation regularities have been found which seem to merit of the isoelectric points of the respiratory proteins of general attention. the invertebrates, now being carried out in this labora• Four types of respiratory proteins are known from tory by Dr. K. 0. Pedersen, has brought to light the blood of the invertebrates, a red pigment another circumstance of considerable importance. (erythrocruorin), a green pigment (chlorocruorin), a He has found that, as a rule, each species is charac• blue pigment (hoomocyanin) and a pigment of reddish terised by a special value of the isoelectric point of brown colour (hoomerythrin). In the following, only its blood pigment. This means that the chemical the first three types will be considered. composition of the blood pigment varies from one Of the erythrocruorin type we have found five species to another, although the mass of the molecule different forms dissolved in the blood and two forms remains practically constant. in blood corpuscles differing with regard to sedi• It seems, therefore, that only a few molecular mentation constant. Each of the five forms of the masses are stable and that it would depend upon the first type is characteristic of one of the following composition of the molecule with regard to various groups of invertebrates: oligochoote worms, poly• amino-acids whether one or the other of the different chrete worms, gastropods, crustaceans, insects. The possibilities is realised. The constancy of the mole• two forms of the second type have been found in the cular weight within a certain animal group would erythrocytes of the capitellide and glyceride worms. then be a measure of the similarity of certain chemical For the chlorocruorin type only one sedimentation processes leading to the formation of the respiratory constant has been observed. For the hoomocyanin protein. type we have found six sedimentation constants The regularities in the sedimentation constants representing the following animal groups : gastro• which we have found seem to justify an effort to pods, cephalopods (two different constants), xiphos• extend this investigation to other species and other urans, crustaceans (three different constants). groups of animals possesRing respiratory proteins. Within some of these groups several species have THE SvEDBERG. been studied, all of which give the same sedimentation ASTRID REDENIUS. constant with a probable error of about 2 per cent. Laboratory of Physical Chemistry, It is not possible to determine the molecular weight University of Uppsala. with the same degree of accuracy, but the fact that Jan. 21. the sedimentation constants agree so closely makes 1 T. Svedberg and Inga-Britta Eriksson, NAT!cRB, H), 4~4. ;-;,•pt. 17, it extremely probable that the molecular weights are 1932. also almost identical. 2 Unpublished determination by l\Iiss I.-B. Eriksson. 3 T. Bvcdbcrg and E. Chirnoaga, J. Amer. Chem. So!' .. 50. J:l99; Among the polychoot,e worms six species belonging 1928. to six different families possess respiratory pigments with the same sedimentation constant, namely, 57 ·5 x 10- 13 (corresponding to a molecular weight" of Virus Diseases and Intracellular Inclusions in Plants 2,850,000). Among the gastropods no less than Vrnus diseases of both plants and animals are eleven species representing seven different families often characterised by the production of abnormal show the same sedimentation constant of 99 ·5 x I0-13 inclusion bodies within the cells of the host. The (corresponding to a molecular weight3 of 5,000,000) bodies are usually of more or less spherical form and and among the crustaceans five species of three are protein in nature. Although they commonly families have the constant 23 ·O x 10 13• The lowest accompany virus diseases, they have not been found sedimentation constant for a to occur in hosts infected with any other type of dissolved in the blood is found for the erythrocruorin disease, nor are they at all similar to the many of the insects (Chironomus larvm). It is only about intracellular inclusions formed in normal healthy half that of the constant of the hoomoglobin of the plants. vertebrates and therefore corresponds to a com• These virus inclusion bodies have attracted much paratively very low molecular weight. Only a few attention and varimrn theories as to their origin and

© 1933 Nature Publishing Group