  We investigate the (reduced) Keller-Segel equations modeling chemotaxis of
bio-organisms. We present a formal derivation and partial rigorous results of
the blowup dynamics of solution of these equations describing the chemotactic
aggregation of the organisms. Our results are confirmed by numerical
simulations and the formula we derive coincides with the formula of Herrero and
Vel\'{a}zquez for specially constructed solutions.
