Last July, just as it appeared the INC. Index might at last cross back into positive ground after lo, these many years, it took quite a Dixie. The steep slide wasn't because business was bad so much as it was a reaction to Wall Streeters' abandoning the risky "story" stocks with which the developing-company INC. list is replete. In the face of falling interest rates, investors turned conservative and sought total-yield situations with dividends and capital gains that, taken together, would return the double-digit payouts they used to be able to get safely in the money market. Now the Index has held its ground for several months and has formed the kind of reversal that quickens the pulses of bullish technical analysts. The Street is kneedeep in cash, not only from domestic investors' recent profits, but from overseas, and it is bound to find its way into speculative stocks. Judging from the chart, the INC. group once again could be poised to accommodate it.