ABSTRACT
The morphological theme of multicellularity and the confluence of generic and genetic processes by which it was achieved in different clades draws attention to questions in microbiology, botany, zoology, and mycology. The relationship between the organism and the cell, and the extent to which an organism's external form (morphology) and internal structure (anatomy) are necessarily interrelated. An evolutionary-developmental perspective in tandem with the growth of molecular biological techniques has informed the pursuit of these and other questions. The patterning processes and the mechanisms accounting for them are the same in different organisms. Another factor is that molecular sequence homology does not necessarily translate into morphogenetic or organographic homology. The cases presented in this chapter are sufficient to show that this is not invariably true and that detailed analyses are required to determine whether two structures or processes are truly developmentally homologous. A third factor is a paucity of phylogenetically disparate model organisms to answer questions that span vastly different life-forms.
