61 
INTRODUCTION. 
The foundation of Darwin’s theory of Natural Selection 
rests on the fact that variation occurs among animals and 
plants of the same species. The underlying cause of this 
variation is absolutely unknown, it is accepted as one of the 
attributes of a species. 
All species are not equally variable. When a genus con- 
tains only a few species which are distinct and not subject to 
much variation the classification is a simple matter. When 
on the other hand it contains many species and their range of 
variation is such that frequently a specimen is found whose 
proper position in the group is uncertain the correct *lassifi- 
cation of such a genus may be a difficult task. When an 
involved genus of this latter type is to be studied it is im- 
perative to obtain large series of specimens from widely 
separated localities and to submit these to a critical examina- 
tion noting and recording every variation that may be ob- 
served. The most important result from a research of this 
kind is the additional and detailed information on the sub- 
ject of variability of species in a state of nature. 
When a species is disposed to vary to a considerable de- 
gree specimens have often been described by different 
workers as new to science and given a new name. The litera- 
ture of Systematic Herpetology contains endless errors of this 
kind. Those made in the last two decades are almost entirely 
due to a faulty appreciation on the part of mere systematists 
of the extent to which some forms may vary. 
From this it follows that one of the sequels to a study 
in variation will often be a contribution to synonymy for it 
will be found that specimens have been described as new that 
are only variations. When two specimens vary one from the 
other yet are connected by intermediate examples it demon- 
strates that they all belong to the same species and therefore 
these variations in no wise merit specific recognition in the 
nomenclature. 
Were the question of nomenclature purely academic 
further reference to the subject would be unnecessary, but this 
assigning of names to each trivial variation and the retaining 
of these names has two pernicious effects: first, it thwarts 
and obscures research along the line of variation, and second- 
ly, it impedes the study of the distribution of animals and 
plants. 
Ih : 
