Unit Characters 
possess latent the character of their dominant 
ancestor. 
Mendelian phenomena force upon us the con- 
clusion that organisms display a number of unit 
characters, each of which behaves in much the 
same way as a radicle does in chemistry, inas- 
much as for one or more of these characters 
others can be substituted without interfering with 
the remaining unit characters. For example, it 
is possible to replace the chemical radicle NH, 
by the radicle Na,; e.g. (NH;),SO, (ammonium 
sulphate) may be transformed into Na,SO, 
(sodium sulphate). 
The conclusion that each organism is com- 
posed of a number of unit characters, which 
sometimes behave more or less independently of 
one another, is one which most biologists who 
have studied the phenomena of inheritance 
appear to have arrived at. Zoologists are mostly 
of opinion that these characters, or rather their 
precursors, exist as units in the fertilised egg. 
Very varied have been the conceptions of the 
nature of these biological units. Almost every 
biologist has given a name to his particular con- 
ception of them. Thus we have the gemmules 
of Darwin, the unit characters of Spencer, the 
biophors of Weismann, the micelle of Naegeli, 
the plastidules of Haeckel, the plasomes of 
Wiesner, the idioblasts of Hertwig, the pangens 
of De Vries, and so on. It is unnecessary to 
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