264 THE AMERICAN NATURALIST. | [Vor. XXXVI. 
independently, or that in the evolution of the teeth cusps should 
arise independently having the same form and position, — what 
criterion should be applied? All such structures are habitually 
regarded as homologous, yet it is apparent that they are not 
derivatives of each other and therefore not homogenous or 
homologous in the strictest sense. 
Such cases of independent evolution of apparently homolo- 
gous organs I recently proposed! to signify as potential, or latent 
homology, borrowing the term “latent”’ from Galton as indica- 
tive of a germinal rather than of a patent or adult character, 
and the physical term “potential” as expressing the innate 
power or capacity to develop a certain organ. But my col- 
league, Prof. Edmund B. Wilson, pointed out to me that such 
cases were almost exactly covered by the original defint- 
tion of the word *homoplasy" by Lankester ('70, p. 42), as 
shown in the subjoined quotations from his essay: 
When identical or nearly similar forces, or environments, act on two or 
more parts of an organism which are exactly or nearly alike, the resulting 
modifications? of the various parts will be exactly or nearly alike. Further, 
if, instead of similar parts in the same organism, we suppose the same 
forces to act on parts in two organisms, which parts are exactly or nearly 
alike and sometimes homogenetic, the resulting correspondences called forth 
in the several parts in the two organisms will be nearly or soci d alike. 
I propose to call this kind of agreement homoplastic or Aomoplasy? . . 
What is put forward here is this : that under the term « homology," belong: 
ing to another philosophy, evolutionists have described and do describe two 
kinds of agreement, — the one, now proposed to be called “homogeny,” 
depending 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 environment on such homogenous parts, or on parts which 
for other reasons offer a likeness of material to begin with. 
Homology thus includes i Hope 
Homogeny. 
It follows that subsequent writers, including myself, have mis- 
used the term “homoplasy,” confusing it with “ parallelism " 
lina communication before the National Academy of Science, Nov. 13, 1901. 
? Ttalics are min: 
3 At this time pcan accepted Herbert Spencer’s Lamarckian views. Sub- 
erasiaka coe ee 
