VII. NON-ISOLABLE RACES. 
22. TRIFOLIUM INCARNATUM QUADRIFOLIUM. 
Few experiences are so well fitted for enabling us to 
obtain an insight into the nature of specific characters as 
the failure of an experiment in selection. I am not speak- 
ing of practical experiments because in such cases the 
breeder is often disappointed by the fact that the result 
is not superior to what he has already, or is not suitable 
for cultivation on a large scale from other causes. This 
kind of failure only concerns the practical breeder and 
does not affect the scientific investigator. The object of 
the latter is simply to find out whether a race specified 
beforehand can be obtained or not. 
According to the theory of selection almost anything 
ought to be obtainable. Almost all characters manifest 
fluctuating variability to the extent requisite for selection. 
If the range of variation is considerable, selection should 
proceed rapidly; if it is within narrower limits it should 
merely require longer series of generations; and if, more- 
over, the familiar but undemonstrated opinion is assumed 
that fluctuating variability increases as the result of the 
selective process, there is no reason why in any given 
case the attempt to breed a desired race should not suc- 
ceed. 
But this discussion, in my opinion, only applies to 
ordinary fluctuating variability, and if thus limited, I 
