200 MENDELISM 
was impossible to rank the individuals into definite 
classes in respect of so indefinite a character as time 
of flowering. On making a perfectly arbitrary division, 
however, it was found that 175 purple and 104 white 
plants were in flower on a certain day, and that 208 
purple and 19 white plants did not open their buds 
until afterwards. There is, therefore, clearly some 
coupling between the presence of white blossoms and 
early flowering on the one hand, and between lateness 
and purple flowers on the other. Two characters 
more diverse than colour of the flowers and time of 
flowering could at first sight scarcely be imagined. 
In this last example the two characters concerned 
do not appear to be completely, but only partially 
coupled. In some cases it is found that the degree 
of partial coupling can be expressed numerically. 
This phenomenon of partial gametic coupling has only 
been discovered very recently, and experiments have 
not been carried far enough to enable us to speak 
about it with any great degree of certainty. But as 
it seems clear that this phenomenon will play an 
important part in the immediate future of genetic 
discovery, it seems necessary to devote some space 
to it, whilst making the proviso that the account may 
require modification within a comparatively short time. 
The phenomenon in question has been observed by 
Bateson and Punnett in crosses between different 
strains of sweet-peas. In the first example the char- 
acters concerned were the shape of the pollen grains, 
whether oval or spherical, and the colour of the flowers, 
whether blue or red. 
