IT has recently been observed1 that the carrier weights, that is, the weight of protein carrying one gram–equivalent of prosthetic group, of a class of conjugated proteins, the chromoproteins, is in many cases equal to the Svedberg unit of about 17,600 gm. In no case is it appreciably less. Data for various conjugated proteins have since become available, and are shown along with the previous data in the accompanying tables. References for the latter data are given in the previous paper1. The carrier weights given include the weights of the prosthetic groups, and are therefore too high. The latter are, however, mostly unknown, but as they are certainly comparatively small (4 per cent in haemoglobin, 1 per cent in the flavins) this error is not serious; moreover, the same systematic error is incurred in calculating the Svedberg unit from ultracentrifugal molecular weight determinations.