  A simple proof of concentration of mass equal to $8\pi$ for blowing up
$N$-symmetric solutions of the Keller--Segel model of chemotaxis in two
dimensions with large $N$ is given. Moreover, a criterion for blowup of
solutions in terms of the radial initial concentrations, related to suitable
Morrey spaces norms, is derived for radial solutions of chemotaxis in several
dimensions. This condition is, in a sense, complementary to the one
guaranteeing the global-in-time existence of solutions.
