No. 424] LATENT OR POTENTIAL HOMOLOGY. 261 
of evolution than is commonly supposed. By parallelism is 
meant the independent acquisition of similar structure in forms 
[2.e., animals] which are themselves nearly related, and by con- 
vergence such acquisition in forms [7.z., animals] which are not 
closely related, and thus in one or more respects come to be 
more nearly alike than were their ancestors." 
The term **homoplasy ” (Lankester) has been long used by 
the writer and others in a somewhat similar sense, but it is 
not equivalent either to “ parallelism” or “convergence.” As 
will be seen below, the fundamental idea is different, because 
homoplasy always involves homology, while parallelism and 
convergence may or may not involve homology. 
ANALOGY IN EVOLUTION. 
Analogous Variation (Darwin). Similar congenital variation in 
more or less distantly related animals and plants. 
Parallelism. Independent similar development of related animals, 
plants, and organs. _ 
Convergence. Independent similar development of unrelated animals, 
ringing them apparently closer together. 
ANALOGY. 
Homoplasy (Lankester) (? Homomorphy, F ürbringer). Independent 
imilar development of homologous organs or regions giving 
rise to similar new parts. 

M 
In brief, analogy embraces similar changes due to similar 
adaptation in function both in homologous and in non-homol- 
ogous organs, both in related and in unrelated animals. 
Tue LIMITED SIGNIFICANCE oF Howorocy. 
Owen ('43, p. 379), Lankester (70), and Fürbringer have 
especially defined and elaborated the very ancient concep- 
tion of homology, as employed by Oken, Geoffroy St. Hilaire, 
and Vicq d'Azyr: homology (Owen, '43), “the same organ in 
“On the Mode of Evolution in the Mammalia " ('91, pp. 363-367), “ parallelism ” 
is used in a very broad sense as affecting the skeleton and teeth, on the principle 
“that identical modifications of structure, constituting evolution of types, have 
supervened on distinct lines of descent,” as embracing not only single characters 
but whole series of them. 
