May 17, 1912] 
Vries. Until within the last two or three 
years the de Vriesian interpretation of 
Mendelian phenomena has been widely 
accepted, especially in England and in 
Germany. Generally speaking, American 
biologists have hesitated to accept the de 
Vriesian doctrine, preferring to regard 
the developed organism not as a structure 
composed of definite elements independent 
of each other in hereditary transmission, 
but rather as a complex resultant of the 
interaction of various cell elements no one 
of which is wholly responsible for any defi- 
nite part of the organism. 
In consonance with the de Vriesian con- 
ception, the idea early developed that the 
organism is a collection of ‘‘unit charac- 
ters’’ arranged in pairs, any one of which 
might be replaced by certain others. Bate- 
son, in 1901, in presenting to the Royal 
Horticultural Society a translation of Men- 
del’s original paper, uses the following 
words: 
In so far as Mendel’s law applies, therefore, the 
conclusion is forced upon us that a living organism 
is a complex of characters, of which some, at least, 
are dissociable and are capable of being replaced 
by others. We reach thus the conception of unit- 
characters, which may be rearranged in the forma- 
tion of the reproductive cells. 
This is the first use of the term unit- 
character the writer has been able to find. 
The idea that hereditary characters are 
indivisible units is, however, due to de 
Vries. In de Vries’s original paper on the 
law of segregation he remarks :? ‘‘ Accord- 
ing to the principles which I have else- 
where announced (Intraceliular Pangen- 
esis), the specific characters of organisms 
are composed of units quite distinet’’; and, 
again, ‘‘for the simple character must be 
considered as an individual unit.’’ The 
term “‘unit-character’’ did not come into 
*T am indebted to Dr. Geo. H. Shull for the 
following citations relating to the history of the 
unit-character conception. 
SCIENCE 
761 
general use until about 1905 or 1906. The 
fact that it presented a conception easily 
apprehended, and the further fact that this 
conception lends itself readily to a con- 
venient system of symbols for representing 
the phenomena concerned, led to the rapid 
adoption of the new phraseology even by 
those who reserved their opinion as to the 
philosophy on which the idea was based. 
We have already seen that Mendel him- 
self referred the phenomena he observed to 
differences in formative elements in the 
germ plasm, which were ‘‘in vital inter- 
action.’’ The de Vriesian philosophy, on 
the other hand, did not place much stress 
on this vital interaction, but looked upon 
each hereditary character of the organism 
as the expression of a particular element 
in the germ plasm which was, more or less 
independently of all others, responsible for 
the development of that character. A pair 
of segregating characters, such as smooth- 
ness and wrinkling in pea seeds, was looked 
upon as due to a corresponding pair of 
pangenes in the germ plasm, one of which, 
if allowed free action, would produce 
smoothness, the other wrinkling. Bateson’s 
term allelomorph was generally used to 
refer to these hypothetical organs in the 
germ plasm, rather than de Vries’s original 
term pangene, since the former term could 
be applied to the visible characters them- 
selves as well. Later, when certain non- 
contrasting characters were found to segre- 
gate from each other, Bateson gave this 
phenomenon the name ‘‘spurious allelo- 
morphism.’’ An example already given of 
such a pair of segregating characters which 
are not contrasted characters is femaleness 
and the barring of the feathers in Ply- 
mouth Rock fowls; this means that when 
the reduction division occurs one of the re- 
sulting cells carries the potentiality of 
femaleness, the other that of producing 
bars on the feathers. Many other instances 
