CHAPTER EIGHT - HOMEOSIS

Summary

Few phenomena are as entrancing as the transformation of one thing into another. The ancients believed that sorcerers had such powers, and modern magicians can still fool children with illusions of this sort. A special class of mutations can actually accomplish this feat.

“Homeosis” means a transformation of one body part into another. The term was coined by William Bateson to describe deformities that are occasionally found in nature. In his classic 1894 monograph, Bateson cataloged 886 abnormal biological specimens, many of which exhibited homeosis. His intent was to investigate how anatomy varies as a way of comprehending how evolution works. This goal was obvious from the book's overtly Darwinian title: “Materials for the Study of Variation Treated with Especial Regard to Discontinuity in the Origin of Species.”

Variation has been supposed to be always continuous and to proceed by minute steps because changes of this kind are so common in variation. Hence it has been inferred that the mode of variation thus commonly observed is universal. That this inference is a wrong one, the facts will show.… The evidence of discontinuous variation suggests that organisms may vary abruptly from the definite form of the type to a form of variety which has also in some measure the character of definiteness. Is it not then possible that the discontinuity of species may be a consequence and expression of the discontinuity of variation?… For the word ‘metamorphy’ I therefore propose to substitute the term homoeosis, which is also more correct; for the essential phenomenon is not that there has merely been a change, but that something has been changed into the likeness of something else.