SMALL E(8) INSTANTONS AND TENSIONLESS NONCRITICAL STRINGS

T-duality is used to extract information on an instanton of zero size in the E(8) x E(8) heterotic string. We discuss the possibility of the appearance of a tensionless anti-self-dual non-critical string throug h an implementation of the mechanism suggested by Strominger of two co incident 5-branes. It is argued that when an instanton shrinks to zero size a tensionless non-critical string appears at the core of the ins tanton. It is further conjectured that the appearance of tensionless s trings in the spectrum leads to new phase transitions in six dimension s in much the same way as massless particles do in four dimensions.