Fig. 5b that the $\rm H\alpha$ E.W. decreases significantly with increasing mass. Although the relation appears noisy and non-linear, low mass systems ($\rm 9< Log~L_H < 10$) show high (40 $\rm \AA$) average E.W., weakly decreasing with mass. The one order of magnitude scatter found in this interval probably reflects the presence or the absence of episods of star formation of short duration which is governed primarily by the local gas instability (see Kennicutt, 1989). At ($\rm Log~L_H > 10$) the $\rm H\alpha$ E.W. drops to zero, with an even higher scatter than in low mass regime. If one divides the data in 3 bins of decreasing $\rm H\alpha$ ($\rm 0<Log H\alpha < 1$; $1<Log H\alpha < 1.6$; $Log H\alpha > 1.6$) the corresponding average $\rm Log~L_H$ are: 10.9; 10.4; 10.0 $\rm L_{\sun}$, i.e. an approximately inverse linear proportionality.

The Dependence of the SFR on the Bulge-to-Disk Ratio
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One of the most clear-cut results of GPB96 is that the presence in the Near-Infrared of centrally peaked structures (bulges-nuclei) strongly correlates with the total H (1.65 $\rm \mu$m) luminosity or mass (see their Fig. 9). These authors used the model-independent parameter $\rm C_{31}$, defined as the ratio of the radii 