This essay explains Anna Seward's famous, vitriolic attacks on the poetic plagiarisms of Charlotte Smith by examining them within the framework of natural history. In the eighteenth and early nineteenth centuries, the vocabularies and methodologies of natural history overlapped with those of literary criticism. Taxonomic concerns with fixity and dynamism, with order and hybridity, permeated Seward's critical endeavors, which were central to her literary reputation. It is my contention that Seward's thinking about literary imitation was shaped by a belief in fixed biological forms. Her response to the zoological texts of the naturalist Erasmus Darwin elucidates her disapproval of Smith's (and Darwin's) poetic borrowings as examples of degenerative, stylistic hybrids. This study thus explores the tendency of Seward and her contemporaries to think in terms of interrelations between biological and poetic forms.