254 MONTGOMERY. [VoL. XII: 
from the specific type, even though they may differ from their 
parents ; so that it is advisable to seek a more general definition. 
Accordingly, organic variation may be defined as growth above 
or below (¢.e. beyond) a given norm ; and organic variability, 
the power of the individual organism to produce such variation. 
Thus we can only then speak of variation when at a particular 
point in the ontogeny the growth of a given organ in one indi- 
vidual is greater or less than the normal growth at that stage. 
It remains necessary, however, to apply distinctive definitions 
to the terms “normal” and “abnormal’’; and, although it is 
not possible to give strictly distinctive definitions to such relative 
ideas, it is, however, generally understood that such characters 
are zormal as are presented by the greater part of the indi- 
viduals of a given species, and such adzormal as are pre- 
sented by a much smaller percentage of individuals. Though 
no really distinctive definitions can be given, the relative mean- 
ings of normal and abnormal are sufficiently understood, which 
is all that our definition of variation demands. And even in 
cases of a more or less perfect intergradation of the degrees of 
development of a given organ, in a large number of individuals 
of a species, it seems to be always possible to show that the 
limits of variation of the large majority of individuals lie within 
a certain circumscribed compass ; so that here normal and 
abnormal degrees of variation may be distinguished.! 
By the expression “ Correlation of the Organs,” is understood 
the state of mutual dependence of the organs, after their divi- 
sion of labor has been brought about by the process of evolu- 
tion ; each has its own particular function to perform, but the 
fulfilment of this function is not sufficient for its existence, 
since rather it would be unable to perform its own function 
without the aid it derives from the other organs. But further, 
1 The term variety is often used ambiguously, as synonymous with variation, or 
as equivalent to the idea subspecies (geographical race). In the strict sense, how- 
ever, the term variety is applicable only to the whole individual, and not toa single 
organ of it, and therefore is not equivalent to variation, which is any growth above 
or below the normal. A variety is then, sevsz stricto, synonymous with the term 
subspecies ; but in order to avoid any possible ambiguity, which has risen from the 
wrong use of the word variety, I shall in the following pages avoid adopting it, 
and shall use instead subspecies, or geographical race. 
