This volume draws attention to the seminal studies and important advances that have shaped systematic and biogeographic thinking and continue to influence its direction today. It traces concepts in homology and classification from the 19th century to the present through the provision of a unique anthology of scientific writings from Goethe, Agassiz, Geoffroy St. Hilaire, Owen, Naef, Zangerl and Nelson, among others. In addition, current attitudes and practices in comparative biology are interrogated, particularly in relation to evolutionary studies leading to a re-statement of the principal aims of the discipline.In order to alert prospective students to pitfalls common in systematics and biogeography, the book highlights three principal messages: biological classifications and their explanatory mechanisms are separate notions; most, if not all, homology concepts pre-date the works of Darwin; and that the foundation of all comparative biology is the concept of relationship - neither 'similarity' nor 'genealogical hypotheses of descent' are sufficient.