The amino-acids of the TMV-wildstrain vulgare, a series of four sequential mutants of it, and of the TMV-wildstrain dahlemense and one mutant of the last were quantitavely estimated by the paper chromatographic method of LEVY. The average values of the Beckman-readings for every amino-acid of the seven strains are given in table I. It could be shown statistically that there was no difference between different preparations of the same strain harvested at various times of the year. There were large differences in the content of eight amino-acids between the two wildstrains, but in addition small yet significant differences between the mutants (see table 4 and 5 for P-values). - If a molecular weight of some 16 000 is accepted for the peptid chain, the repeating subunit of the TMV protein shell, we found parallel with the mutation vulgare ➝ flavum two aspartic acid substituents replaced by one alanine and one valine per chain; with the mutation step flavum. ➝ necans one alanine was changed to one phenylalanine, with necans ➝ revirescens one valin lost and one aspartic acid gained, and with dahlemense ➝ luridum one glutamic acid replaced by one leucine (table 6).