variation in the former over the latter.  The cases in which this relation is reversed are found, as before, in comparing the simple interval with the duration of the unit group; and the exceptional instances are just those, namely the first and third forms, in which the mean variation of this uncompounded interval is itself at a minimum.  This means that the simple interval presents a more mobile character than that of the group; and while in general it is less stable than the latter, it is also the first to show the influence of increased cooerdination.  Training affects more readily the single element than the composite measure, and in the most highly cooerdinated forms of rhythm the simple interval is itself the most perfectly integrated unit in the system of reactions.

Here, as in the preceding rhythmical forms, evidence of higher grouping appears in the alternate increase and decrease of mean variation as we pass from the first to the second subgroup when the material is arranged in series of eight beats.  The proportional values of the indices are given in the following table: 

TABLE LXXVI.

Subgroups  Init.  Stress   Sec.  Stress   Tert.  Stress   Fin.  Stress
1st Four,      1.000         1.000          1.000         1.000
2d Four,       0.950         0.762          0.984         0.790

The first member of the larger group, in the case of every rhythm form here in question, is less exactly cooerdinated than the second, the interpretation of which fact need not here be repeated.  Several additional points, however, are to be noted.  The differences in stability of cooerdination which are encountered as one passes from the first to the last of the four rhythm forms, extends, when the reactions are analyzed in series of eight beats, to both members of the compound group, but not in equal ratios.  The mean variation of the second and fourth forms is greater, both in the first and second subgroups, than that of the corresponding subgroups of the first and third forms; but this increase is greatest in the first member of the composite group.  That is, as the group grows more unstable it does so mainly through an increase in variation of its initial member; or, in other words, the difference in variability of the beat intervals of the first and last subgroups reaches its maximum in those rhythmic types in which the indices of mean variation for these intervals are themselves at their maxima.

This process of cooerdination, with its indication of a higher rhythmical synthesis, appears also in the transformations in the value of the mean variations in duration of the total groups, when the material is treated in series of eight beats, as in table LXXVII.

TABLE LXXVII.

Subgroups.    Init.  Stress.    Sec.  Stress.    Tert.  Stress.    Final Stress.
1st Four,         1.000          1.000           1.000           1.000
2d Four,          0.773          0.768           0.943           0.579

The total initial group, therefore, as well as each of its constituent intervals, is less stable than the second.