ANTIGEN VARIATION IN PARAMECIUM AURELIA, VARIETY 1

recent years the iniportance of the cytoplasm as a determinant of hereditll:it the cytoplasm contains genetic units as ;iutononioiis and specific as the 11ucle;ir geiies, though such claiiiis ]lave been ni~ich disputed. l'arainecium is csccp~ioiially s1iit;ible for the iiivcstigatioii of this probleui, aiid thanks to the \\orlc of SON NEHOKN and his colleagues a considerable aiiiouiit of information conceriiiiig the effect of cytoplasiiiic materials 011 certain characters of the orgaiiism, such as the "killers" and the antigens, has been obtained.