Abstract. Let F be a homotopy functor with values in the category of spectra. We show that partially stabilized cross-effects of F have an action of a certain operad. For functors from based spaces to spectra, it is the Koszul dual of the little discs operad. For functors from spectra to spectra it is a desuspension of the commutative operad. It follows that the Goodwillie derivatives of F are a right module over a certain 'pro-operad'. For functors from spaces to spectra, the pro-operad is a resolution of the topological Lie operad. For functors from spectra to spectra, it is a resolution of the trivial operad. We show that the Taylor tower of the functor F can be reconstructed from this structure on the derivatives.Let C and D each be either the category of based topological spaces, or the category of spectra. Let F : C → D be a homotopy functor. Goodwillie's homotopy calculus provides a systematic way to decompose F into homogeneous pieces which are classified by certain spectra with Σ n actions, denoted ∂ n F and, by analogy with ordinary calculus, called the derivatives or Taylor coefficients of F .A key problem in the homotopy calculus is to describe all the relevant structure on the symmetric sequence ∂ * F , and to reconstruct the original functor F (or at least its Taylor tower) from this structure. In [2] we gave a general description of this structure. In this paper we give an alternative description of the structure on ∂ * F in cases when F takes values in the category of spectra. We interpret this structure as that of a 'module over a pro-operad'. The structure arises from actions of certain operads on the partially stablized cross-effects of F . Thus we connect the module structure on ∂ * F with Goodwillie's presentation of ∂ * F as stablized cross-effects of F .Let us review briefly our previous results on the subject. Let I Top * be the identity functor on the category of based spaces. It was shown by the second author in [5] that ∂ * I Top * has an operad structure. In fact, ∂ * I Top * is a topological realization of the classical Lie operad, and we refer to ∂ * I Top * informally as the topological Lie operad. In [1] we showed that for a functor F : Top f * → Sp, the symmetric sequence ∂ * F is a right module over ∂ * I Top * . We also remarked in [1] that the module structure was not sufficient for recovering the Taylor tower of F , and therefore there had to be additional structure, that still had to be described. In [2] we gave a description of this extra information. Specifically, we constructed a comonad C, defined on the category of right ∂ * I Top * -modules, which acts on the derivatives of a homotopy functor F . We showed that the Taylor tower of F can be recovered from this action.The methods of [2] were quite general (applying to functors between any combinations of the categories of based spaces and spectra). The comonad C has the form ∂ * Φ, where ∂ * is Goodwillie differentiation, and Φ is a functor right adjoint to ∂ * . In this paper we provide a more concrete description of t...