  A previously successful dispersive method has been applied to understand
different values for $R(\sqrt{s} = 5 \div 7.5 GeV)$ obtained by MARK I and
Crystal Ball collaborations. We compute $R$ in the disputed region with data
from outside this region and asymptotic behavior given by the standard model
with 5 quark flavors, and find agreement with the Crystal Ball result. On the
other hand, the MARK I data are reproduced if we augment the asymptotic
behavior with contributions from a single spin zero quark of charge ($ -1/3$).
The visible hadronic fragments from such scalar quarks are not likely to
produce predominantly pure 2-jet events at such low energies. Hence, such decay
modes may have been removed by the Crystal Ball energy imbalance cuts in their
definition of hadronic events but not in MARK I events, thus accounting for the
discrepancy in the two results. Upper bounds on spin zero quark production at
LEP through $Z$ decay data are used to estimate the mixing angle between $T_3\
= -1/2$ and $T_3 = 0$ scalar quarks. Recent negative results about spin zero
quarks from CLEO are critically examined. We briefly discuss diquark production
hypothesis and find it very unlikely to explain the discrepancy.
