G. J. DR FEJ ÉRVÁR Y 
482 
though correct, must be limited by certain restrictions, as is also 
the author’s intention, and cannot be generalized. For, as 
regards Varanus, a generalization of the theory would lead to a research 
of their land of origin in India, and that would not agree with palaeonto¬ 
logical facts i The difficulty of drawing conclusions from variations lies 
furthermore in the fact that certain species or forms may vary in a much 
lesser degree even within a smaller group, than others, most 
closely related to them; the same fauna-territory .may therefore be ' 
inhabited as well by epistatic as by intensely developing forms, belonging 
both to the same genus. The fact of seve r a 1 species living on the same 
territory, offers thus no reason from which to conclude to the whole 
g roup in question having risen or long since acclimatized itself in 
those regions, as the formation of species always depends on the various 
biological influences produced on the forms in question by the terri¬ 
tories reached in the course of geographical expansion ; these forms 
naturally might again prove sensitive or indifferent to the respective 
influences. In connexion with these phenomena no great result can 
therefore be obtained with regard to the geographical distribution 
of the Varanidae ; some species must certainly be considered 
as younger branches, as V. prasinus (Müll.) Schleg. for instance; 
on the whole however the genus Varanus is the subsisting member 
of a most ancient and isolated group, presenting but very little variation. 
This is also proved by the fact that Varanus species have, so to say, no 
varieties. The whole genus in general being composed of stabilised and 
definitely limited species. A biological explanation of its most flourishing 
development having been reached in South-Eastern Asia, can only be given 
by the fact of that territory being the most favourable to its sub¬ 
sistence and development. This explanation, although without doubt most 
vague and general in character, is nevertheless the only one which can 
be presently given for the abundance of species in South-Western Asia. 
I have not been able to throw light on the question why in Africa 
so small a number of Varanus live scattered on such an exten¬ 
sive territory (Text fig. 24), what could almost be taken for a contra¬ 
diction, met with moreover in the same form amongst other faunistica! 
groups, although conformity in effects can nowise justify a conclusion to 
identity of causes, which in this case may be of exceedingly heterogeneous 
nature. Compared to the Asiatic, the African fauna presents a certain 
monotony of character. So much however it seems justifiable to admit, 
considering the absence of Varanus in Madagascar, also emphasized by 
Gàdow 1 , that, as has been already remarked, these reptiles must have 
1 Gadow, op. cit., p. »543. 
