Conics -- Complete conics -- Systems of conics -- Equations of the degeneration hypersurfaces -- Conditions imposed on conics -- Action of the projective group and proper solutions of an enumarative problem -- Genericity of the data of conditions -- Local characters of a condition -- Halphen's first formula -- Computation of characteristic numbers -- Examples -- Strict equivalence of conditions -- Systems of conics contained in Sp,q -- Conics satisfying five independent conditions -- Cycles on W and on B -- Multiplicity cycles and Noether's formula -- Improper intersection numbers -- Generalization of Halphen's formula to conditions of higher order -- Examples of higher order conditions -- Strict equivalence of conditions -- Enumerative ring of W -- Computation of products in halยท (W) -- Further examples