In this essay I argue that Hegel's system includes no ontology of nature, either in any traditional sense, or in any specifically Hegelian sense, of "ontology." What Hegel provides instead is a philosophy of nature in which specifically natural activities generate specifically natural differences and identities out of themselves. I make my case first by considering the meaning of "ontology" Hegel inherited from Wolff and Kant. I show that Hegel rejected this sense of ontology for his own philosophy, in part because of his recognition of the success of the Kantian critical project in making traditional ontology impossible. I then argue that although Hegel sometimes characterizes his own Objective Logic in ontological terms, he also restricts that characterization in a way that makes it inapplicable to his treatment of apparently natural categories in the Logic itself, and to his Philosophy of Nature. Against this anti-ontological background I examine a small portion of Hegel's concrete treatment of natural phenomena and kinds: his discussion of the nervous system in higher-order animals. Through its self-formation and the contribution of its nervous-system activity to its overall life, the animal does not implement differences, identities, or logical structures borrowed from elsewhere, but itself produces the differences and identities through which it is constituted. The self-determination Hegel articulates in his study of the nervous system gives us a good example of his typically "on-the-ground" approach, which is strikingly different from the "top-down" approach more common in the ontological tradition.