Field homology: A meaningless concept

Most biological homologues involve comparison of single characters in two o r more taxa. It is possible, however, to recognize homologous characters be tween two or more taxa that involve the transformation of one character int o many characters or many characters into one character. This type of homol ogy is recognized as field homology and it has been widely used in comparat ive neuroanatomy. The emergence of the cladistic analysis of embryonic stag es in the development of neural characters, however, strongly suggests that field homology is a meaningless concept. When it appears necessary to reco gnize field homologues, it is because comparisons are being made at an inap propriate level within a given biological hierarchy. Furthermore, recogniti on of field homologues restricts evolutionary mechanisms to a single mechan ism of parcellation as defined by Ebbesson.