436 Brian K. Hall
one case, acting ontwo or more parts of an organism(what had been called from
Owen on, serial homology), in the other acting onparts in two organisms,the
parts being exactly or nearly alike: “Homoplasy includes all cases of close resem-
blance of form which are not traceable to homogeny, alldetailsof agreement not
homogenous in structures which are broadly homogenous, as well as in structures
having no genetic affinity [i.e., no connection through descent]” [Lankester, 1870a,
41].
Lankester made it very clear that homogeny and homoplasy weretwo classes of
homology: “What is put forward here is this, — that under the term “homology”,
belonging to another philosophy, evolutionists have described and do describe two
kinds of agreement — the one, now proposed to be called “homogeny”, depend-
ing simply on the inheritance of a common part, the other, proposed to be called
“homoplasy”, depending on a common action of evoking causes or moulding en-
vironment on such homogenous parts, or on parts which for other reasons offer a
likeness of material to begin with” [Lankester, 1870a, 42]. Equally clear was the
reason for separating the two: “Darwinian morphology has further rendered nec-
essary the introduction of the terms “homoplasy” and “homoplastic” to express
that close agreement informwhich may be attained in the course of evolutionary
changes by organs or parts in two animals which have been subjected to similar
moulding conditions of the environment, but have not close genetic community of
origin [ancestry], to account for their similarity in form and structure” [Lankester,
1911, vol. 28, 1029].
Lankester’s term homogeny did not take hold.^15 Homoplasy — similarity re-
sulting from evolutionary convergence, parallelism or reversal — has endured, as
exemplified in the bookHomoplasy: The Recurrence of Similarity in Evolution,
edited by Sanderson and Hufford [1996], produced under the expert editorial direc-
tion of Charles (Chuck) Crumly of Academic Press to parallel (no pun intended)
Homology: The Hierarchical Basis of Comparative Biology, edited by Hall [1994a].
Adverse reaction to homogeny was rapid, especially from St. George Mivart
who responded in the very next issue ofThe Annals and Magazine of Natural
History, the journal in which Lankester had published his paper. Lankester [1870b]
responded in the same issue; see Hall [2003a] for details. Mivart thought that
abandoning the term homology would be “prejudicial to science”, that “it is quite
possible to have, on the one hand, developmental homogeny between parts which
are not ancestrally homogenous, and, on the other, to have ancestral homogeny
between parts which are not developmental homogenous” [Mivart, 1870, 116],
and proposed 25 different types of homology to support his arguments. A year
(^15) Lankester introduced the termhomotrophicfor what Darwin [1910] had discussed as cor-
relations, compensation and economy of growth, which, for Lankester [1870a, 39] reflected the
“delicate balancing of the forces of the organism, which would cause the disturbance of equi-
librium in one part to affect simultaneously another part equally and similarly. Organs which
stand in this nutritional relation to one another may be termed homotrophic”. The term has
not survived, although the notion underlying it is important, reflecting as it does pleiotropy,
epistasis, embryonic inductive interactions, and constraint [Raff, 1996; Hall, 1983; 1999a; Burian
et al., 2000; Hall, 1999a; 2001a; Robertet al., 2001; Hall and Olson, 2003].