1921 .] 
537 
Subspecies and Evolution. 
5. Definition of a subspecies. 
There can be no hard-and-fast definition for a state of 
nature which is constantly changing. There exist forms 
which we all know, whose status is still unsatisfactory, and 
even Nature herself might have difficulty in defining them 
as species or subspecies, for the simple reason that they are 
in the transitional stage between the two. 
But it seems correct to describe trinomially as geo¬ 
graphical races those birds of similar type inhabiting 
different geographical areas, and whose differences are 
abundantly (not exclusively) constant within a given area. 
In fact, they must be a pure geographical variation, the 
variation coinciding with distribution. 
Intermediate forms will nearly always be found in inter¬ 
mediate areas, but such need not always be the case, as in 
the instance of a race which has receded from its parent 
stock into temporary isolation, and which has again ex¬ 
panded towards its parent stock. Such appears to be the 
case with Corvus f. frugilegus and Corvus f. pastinalor , and 
perhaps with Erolia minuta and Erolia ruficollis. Opinion is 
bound to differ regarding the status of such forms, as the 
question is a pure matter of opinion and not of fact. 
Again, it is frequently stated that two geographical races 
of the same species must not breed in the same area. We 
agree that a geographical race is destroyed if another race 
of the same species continually breeds over a wide area of 
the former ; but where two races of the same bird meet, they 
naturally, either by mating together or under the influence 
of intermediate conditions, produce intermediate forms. In 
fact, where this occurs it is good proof of the two races 
being good geographical races of the same species. 
This short article is not intended to be a treatise on 
evolution. It has been written in the hopes that it may 
form the basis of a discussion in which we may have the 
opportunity to take part at some future meeting of the 
British Ornithologists’ Club. To the highly-trained scientific 
mind, many of my contentions are no doubt ridiculous and 
untenable. It is the truth we seek, and if from the fallacies 
in my arguments others can point to more truthful causes of 
evolution, my time will not have been wasted. 
2 n 2 
