Homology and Homoplasy 433selection, where the issue is not definitional but more fundamental and related
to the existence, mode of operation and role of natural selection. Mivart [1870]
proposed twenty-five terms for subclasses of homology; Panchen [1992] listed nine
under the transformational and taxic homology, while from his studies on plants,
Sattler [1984] argued that we should replace the term homology with similarity,
structural correspondence or structural relationship. Nineteen types are listed
in the index to Hall [1994a], yet others in Haas and Simpson [1946] and Fitch
[2000]. The man who provided the most rational subdivision of homology, E. Ray
Lankester, proposed only a single new definition, but unlike so many others it
embodied a new approach and a conceptual advance.
Karl Gegenbaur also converted to a post-Darwinian homology ([Szarski, 1949];
[Di Gregorio, 1995]). Gegenbaur [1859] considered homologies to be shared struc-
tural types. Eleven years later, having absorbed Darwin’sThe Origin of Species,
Gegenbaur ([1870], translated 1878) had added common ancestry and common em-
bryonic rudiments to his definition: “das Verhltniss zwischen zwei Organen, die
gleichen Abstammung besitzen somit aus der gleichen Anlage hervorgegangen sind”
[the relationship between two organs that share common origin (ancestry) and
therefore were derived from the same anlagen (primordium)]. Lankester [1870a],
like Gegenbaur, emphasized common ancestry. Indeed, Lankester favoured aban-
doning the term homology altogether, proposing in its place ‘homogeny’ for simi-
larity resulting from shared ancestry (see below).
5.1 Homology, Archetypes and Embryonic Development
Richard Owen’s approach to homology was informed (but not straitjacketed) by
embryonic development, especially the researches of Rathke [1839] and Huxley
[1864] on the development of the skull of ‘the’ lamprey, considered to be the
primitive vertebrate skull. Owen used these studies to develop his theory of the
archetypal vertebrate skull and to extend the concept of the archetype as an ab-
stracted or ideal form to the vertebral column and limbs and then to the entire
vertebrated animal [Owen, 1846; 1848; 1849].^11 Owen’s archetype was grounded
solidly in embryology, specifically in the ‘laws’ of Karl Ernst von Baer (Box 2) as
introduced into England by a Scottish physician, Martin Barry [1836-1837a,b] and
an English physiologist, William Carpenter [1839].
Initially, Darwin was with Owen on the archetype, seeing Owen’s archetype as
theancestral vertebrate. Darwin moved to an embryological — and therefore more
mechanistic — view of the archetype. As he recounted to Huxley, “The discovery
of the type or ‘idea’ (inyoursense, for I detest the word as used by Owen, Agassiz
(^11) The term archetype was introduced simultaneously and independently by Owen [1846] and by
the London anatomist, Joseph Maclise [1846], both of whom saw identification of the archetype
as the primary aim of comparative anatomy. For recent analyses see Desmond [1982], Hall
[1992; 1994a], Rupke [1993; 1994], Bowler [1996] and Padian [1997]. For a modern version of
the necessity of an archetypal concept in morphology, and more specifically in homology, see
Young [1993]. For the development of a science of morphology, see M. H. Wake [2001], Wake
and Summers [2003] and Hall [2005c].