THE TROPtCS. 
m 
followed in the formation of the gametes. And we are led to 
perceive that many apparent exceptions to Mendel’s Law will 
require very careful study before it can be definitely stated 
that they follow any other method of gamete formation. 
VII.—CORRELA TION. 
The cases so far cited of phenomena which extend beyond 
the limits of Mendel’s original observations have all had 
relation to dominance, or to the visible expression of the 
characters in zygotic organisms. An important series of 
real exceptions to Mendel’s Law, as to the behaviour of the 
germinal representatives of characters during the process of 
formation of the gametes, is afforded by cases of correlation. 
One such case at least was already known to Mendel, for in 
his own experiments coloured flowers, purple spots in the 
axils of the leaves, and coloured seed coats always appeared 
together on the same plants. 
For such a case of correlation as that between coloured 
flowers and coloured axils Oorrens uses the term “ semi-in¬ 
dependent ” (halbselbstandig)—both characters depend upon 
the formation of anthocyan, but each has its own independent 
position. In the case of “ conjugate” characters (conjugirt), 
two or more characters, belonging to separate categories and 
each conceived as possessing an “ Anlage ” of its own. 
remain together during the formation of the gametes. 
Correns himself points out that these two forms of corre¬ 
lation are not always easy to distinguish; moreover, it is 
somewhat doubtful how far we are yet justified in describing 
the particular behaviour of “ Anlagen.” 
The following case would no doubt be ranked by Correns 
as an example of conjugate characters : — 
Example IX .—A clear case of correlation was observed 
between the time of flowering on the one hand and the 
colour of the flowers (axils and seed coats) on the other. 
