Is the definition of homology circular?
Wells spends this entire chapter thoroughly confused about homology, and does his best to confuse his readers as well. About five minutes of research by yours truly turned up a perfectly reasonable discussion of homology (Amundson, 2001) which nicely straightens things out: in a nutshell, homology is detailed similarity of organization that is functionally unnecessary, meaning the similarity is unnecessary (the trait in question may be, and usually is, functional).
