No. 424.] LATENT OR POTENTIAL HOMOLOGY. 269 
at similar points and presenting a latent homology or homoplasy. 
The record in the upper molar teeth stands thus : 
HOMOLOGY. 
AEE v S TT PAG -ETTE 
HOMOGENY ‘ HOMOPLASY 

Cusps or folds which are or may be 
independently developed in dif- 
Primitive three cusps common to 
ali ferent orders. 
ammals. 
Protocone ypocone 
aracone Metaconule 
Metacone Protoconule 
—- arastyle 
— Hypostyle 
This expresses the comparison of mammals as a whole. 
Within many of the orders, such as the Perissodactyla, which 
arise from six cusped ancestors, the homology is different. 

HonoLocv. 
eS a (rite NI. een 
HOMOGENY HOMOPLASY 
Protocone Parastyle 
Paracone Mesostyle 
Metacone Crista 
Hypocone Crochet 
Protoconule Antecrochet, etc. 
Metaconule diss 
The elements to which these terms are applied are best 
exemplified in the molar teeth of some of the primitive horses 
(Fig. 6). 
The teeth are by no means the only structures which evolve 
under this principle, the skull, vertebral column, and limbs also 
evolving under it more or less completely; but the teeth afford , 
a singularly beautiful illustration of it because they exclude 
individual modification. 
