June, 1906.] 
Terminology of Organs. 
543 
6. Imperfectly developed or reduced organs of all types 
mav be called rudimentary organs or rudiments. So long then 
as the nature of any incomplete organ is unknown, or speaking 
generally, it may be called a rudimentary organ ; but with complete 
knowledge, and speaking specifically, it will be called an incipient, 
a nascent, a vestigial, an abortive, or an atrophied organ as the 
case may be. 
Definition — Rudimentary organ, rudiment (Lat. rudimentum) 
— An organ in the initial, incipient, or incomplete stage of develop- 
ment; or one that has become reduced either in the history of 
the race or of the individual. 
There are still other types or conditions of organs which may 
be defined in a definite sense ; 
1. Atavistic organs are such as show in the individual a re- 
turn to some ancestral type. 
2. Retrogressive organs are such as are passing from a 
higher to a lower or less perfectly developed condition or state of 
organization. 
3. Abnormal organs are those which deviate from the usual 
tvpe in some extraordinary way, as in shape, size, number of 
parts, color or other character. Good examples of abnormal 
organs are shown in the following: a fasciated stem, a three-parted 
Fuchsia, or a “web-toed” man. Abnormalities are frequently 
inherited. 
4. Under the term malformed organs, may be included such 
tvpes as unusual growths due directly to some external condition 
in the life of the individual, as ari insect bud-gall, or a leaf blade 
of a rhubarb grown in the dark. A good example is a pointed 
leaf which has become emarginate through some accident dur- 
ing its development. A malformation cannot be transmitted 
unless acquired characters so called are inheritable. 
5. Transformed organs are such as show a change in the in- 
dividual or the race from one type of structure or function to an- 
other. A stamen developing into a petal is a transformed organ. 
In such transformations there is a failure of the usual hereditary 
tendencies to assert themselves while other tendencies present 
in the same cells become dominant when they should be sup- 
pressed. Insect wings are probably transformed gills and rep- 
tilian lungs transformed air-bladders. 
6. Under the term “juvenile organs” may be included all 
organs which appear on the young individual but which are ab- 
sent in the adult. They may be special organs of the embryo, 
or normally developed organs which later drop off or are absorbed. 
The compound leaves of certain seedling Acacias which in the 
adult stage have only phyllodes are good examples of juvenile 
organs; the tail of a tadpole is a juvenile organ. The term em- 
bryonic organ may be used for the earlier stage whenever there 
