IHE 
AMERICAN NATURALIST 


VoL. XXXVI. April, 1902. No. 424. 


HOMOPLASY AS A LAW OF LATENT OR 
POTENTIAL HOMOLOGY. 
HENRY FAIRFIELD OSBORN. 
My study of teeth in a great many phyla of Mammalia in past times has con- 
vinced me that there are fundamental predispositions to vary in certain directions ; 
that the evolution of the teeth is marked out beforehand by hereditary influences 
which extend back hundreds of thousands of years. These predispositions are 
aroused under certain exciting causes and the progress of tooth development takes 
a certain form SORTE into actuality what has hitherto been potentiality. 
Science, N.S., Vol. VI, No. 146 (Oct. 15, 1897), pp. 583-587. 
IN previous communications, as shown in the above quota- 
tion, I have spoken of the * potential of similar variation," as 
covering cases of the independent evolution of identical struc- 
tures in the teeth of different families of mammals, especially in 
relation to the homologous “ antecrochet " and “ crochet ” folds 
in the teeth of horses, rhinoceroses, and we may now add, of 
titanotheres (Osborn, '94, p. 208). In the present commu- 
nication I propose to treat somewhat more fully of the same 
phenomenon, as a special form of homology which has been 
clearly defined by Lankester in 1874 as homoplasy, but into 
which poleoptelogy h has. brought the idea of “ potential. n 
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