542 
The Ohio Naturalist. 
[Vol. VI, No. 8, 
properly called “nascent” organs. Thus the lung of a reptile 
must at one time have been a nascent lung while gills were used 
to aerate the blood. The hypophysis of a moss is a nascent leaf 
whether it ever develops any further or not. Such organs were 
called “prophetic” by Agassiz in harmony with his theory of 
creation. If a noun is to be used it appears to the writer that 
“primordium” is the correct expression. Thus “primordial 
organ” becomes synonymous with “nascent organ” and should 
perhaps have the preference. 
Definition — Nascent organ (Lat. nasci, nascens) — An organ at 
the beginning of its evolution or at the beginning of its develop- 
ment in the race; an organ in its first stages of evolution as com- 
pared with other homologous organs. 
3. If an organ was developed in the past but is now contin- 
ually imperfect or undeveloped in the individuals of a species it 
is called a “vestigial” organ or a “vestige.” The three small 
sterile stamens in a Catalpa flower are vestigial. The splint 
bones in a horse and the dew-claws on a cow’s foot are examples 
of vestigial organs. Such organs even if no longer functional 
may still be useful. Some undeveloped organs may however not 
be vestigial. The incepts may be present in the embryonic state 
of the individual and may or may not develop, depending on 
the sex determined during the development of the organism. 
Such organs may in some cases be vestigial or they may only be 
special cases of abortion. 
Definition — Vestigial organ, vestige (Lat. vestigium) — An 
organ which was normally developed in the past history of the 
race but which has become permanently reduced, never develop- 
ing completely in any individual. 
4. If an organ normal in the species fails to develop properly 
in an individual it may be called an abortive organ. A micro- 
cephalic individual has an abortive head. A flower bud or a leaf 
may be abortive by reason of an unfavorable position on the 
stem. Abortive organs may sometimes be atavistic, the devel- 
opment having stopped at a stage representing a more primitive 
condition of the race. Abortive should not be used in the sense 
of vestigial. 
Definition — Abortive organ (Lat. abortare, abortivus) — An or- 
gan normal in the species but which has failed to reach full de- 
velopment in the individual. 
5. Organs properly developed in the individual sometimes 
become reduced through disease or other causes. Such organs 
are properly called “atrophied” organs. 
Definition — Atrophied organ (Gr. a trophia) — An organ which 
is normal in the species and fully developed in the individual, 
but which has become reduced through pathological conditions 
or through disuse. 
