  In this paper, we report our studies on the gaseous and chemical properties
of a relatively large sample (53 members) of blue compact dwarf galaxies
(BCDs). The results of correlations among the oxygen abundance, stellar mass,
gas mass, baryonic mass, and gas fraction are present both for E- and I-type
BCDs, which are classified according to Loose & Thuan (1985) and show
elliptical and irregular outer haloes, respectively. These correlations of
I-type BCDs show similar slopes to those of E-type ones. However, in general,
E-type BCDs are more gas-poor and metal-rich than I-type ones at a given
baryonic mass. Based on these results, we suggest that E-type BCDs, at least a
part of them, and I-type ones might be likely at different evolutionary phases
and/or having different progenitors. Our investigation of the correlation
between oxygen abundance and gas fraction shows that BCDs appear to have not
evolved as isolated systems, but to have experienced some gas flows and/or
mergers.
