504 TRANSACTIONS OF SECTION D. 
I suggest an elastic terminology for the various resemblances indicative of 
the degree of homology of the respective organs, the degree of affinity of their 
“owners, and lastly the degree of the structural likeness attained. 
Homogeny.—The structural feature is invented once and is transmitted, with- 
out a break, to the descendants, in which it remains unaltered, or it changes by 
mutation or by divergence, neither of which changes can bring the ultimate 
results nearer to each other. Nor can their owners become more like each other, 
since the respective character made its first appearance either in one individual, 
or, more probably, in many of one and the same homogenous community. 
Homoplasy.—The feature or character is invented more than once, and 
independently. This phenomenon excludes absolute identity; it implies some 
unlikeness due to some difference in the material, and there is further the 
chance of the two or more inventions, and therefore also of their owners, 
becoming more like each other than they were before. 
CATEGORIES OF HOMOPLASY. 
Tsotely.—l{ the character, feature, or organ has been evolved out of 
homologous parts or material, as is most likely the case in closely related groups, 
and if the subsequent modifications proceed by similar stages and means, there 
is a fair probability or chance of very close resemblance. Jso-tely: the same 
mark has been hit. 
Homeotely.—Although the feature has been evolved from homologous parts 
or material, the subsequent modifications may proceed by different stages and 
means, and the ultimate resemblance will be less close, and deficient in detail. 
Such cases are most likely to happen between groups of less close affinity, 
whether separated by distance or by time. Hom«o-tely: the same end has 
been fairly well attained. The target has been hit, but not the mark. 
Parately.—The feature has been evolved from parts and material so different 
that there is scarcely any or no relationship. The resulting resemblance will 
at best be more or less superficial ; sometimes a sham, although appealing to our 
fancy. Para-tely: the neighbouring target has been hit, 
EXAMPLES, 
Isotely: Bill of the Ardeidce Baleeniceps (Africa) and Cancroma (Tropical 
America). 
Zygodactyle foot of Cuckoos, Parrots, Woodpeckers (73). 
Patterns and coloration of Ylaps and other snakes. 
Parachute of Petawrus (marsupial) ; Pteromys (rodent) and Galcopithecus. 
Perissodactylism of Zitopterna and Hippoids. 
Bulla auris of Plioplatycarpus (Pythonomorph) and certain Whales; if 
tympanic — quadrate. 
Grasping instruments or nippers in Arthropods: pedipalps of Phryne; chele 
of Squill; first pair of Mantis’ legs. 
General appearance of Moles and WNotoryctes, if both considered as 
mammals; of Gulls and Petrels, if considered as birds. 
Homeotely : Heterodactyle foot of Trogons Ga) , 
Jumping foot of AMacropus, Dipus, Tarsius. 
Intertarsal and cruro-tarsal joint. 
Fusion and elongation of the three middle metarsals of Dipus and Rhea. 
Paddles of Ichthyosaurs. Turtles, Whales, Penguins. 
‘Wings’ of Pterosaurs and Bats. 
Long flexible bill of Apterya and Snipes. 
Proteroglyph dentition of Cobras and Solenoglyph dentition of Vipers. 
Loss of the shell of Limaz and Aplysia. 
Complex molar pattern of Horse and Cow. 
Parately : Bivalve shell of Brachiopods and Lamellibranchs. 
Stretcher-sesamoid bone of Pterodactyls (radial carpal); of Flying Squirrels 
(on pisiform) ; of Anomalurus (on olecranon). 
Bulla auris of Pythonomorph (quadrate) and Whale (tympanic); is incus= 
quadrate. ; : 
‘Wings’ of Pterosaurs, or Bats, and Birds. 
