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 2 ; e.g. (NH 3 ) 2 SO 4 (ammonium 

 sulphate) may be transformed into Na 2 SO 4 

 (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 micellae 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 



