130 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XVII. 



When we come to ara^se the remainder we find they practically fall 

 into three classes :— 



(1) " Species " which have been described from single specimens 

 which exhibit no structural peculiarity and which should in most 

 cases be treated as sports of the nearest known form until other 

 specimens and both sexes have been captured. 



(2) Nearly allied forms which appear to be complementary to 

 each other through a series of geographical regions orsubregions 

 and whose distribution does not overlap (ignoring casuals of 

 a single season) though it may be discontinuous. 



(3) Forms or groups of forms of very wide distribution, all or 

 most of which can often be obtained in one locality. 



The problem of how to deal with these can only be solved by a care- 

 ful study of the Laws of Variation. These of course cannot be dealt 

 with in detail in the limits of a single article, but the writer has attempt- 

 ed to express his own views on the subject as bearing on our problem 

 in an aphoristic form for the sake of brevity. 



(1) Most variable types are those not confined to one particular 

 region of distribution but continuously distributed through the 

 neighbouring regions. 



(2) The next most variable are those found practically throughout 

 a particular geographical region. 



(3) Those restricted to a subregion are much more constant. 



(4) Those confined to a minor division or to two or more small 

 discontinuous areas are generally very constant and often imper- 

 vious even to seasonable changes. 



(5) The variability of (1) and (2) differs in kind as we]] as degree, 

 whereas that of (1) is so great that it is difficult to define, except 

 in the broadest liues, a type to which all the specimens captured 

 even in a single locality will conform; in (2) the types are fairly 

 constant in particular areas but vary geographically in the 

 various subregions and for minor subdivisions of its area of 

 distribution, such variations often proving on investigation to be 

 as much climatic, or dependent on the rainfall, as geographical. 



So long as (1) types maintain their wide distribution the irregularity 

 is at least partly maintained by migrations and counter-migrations 

 keeping the blood in fusion. 



(6) Geographical variations are dependent on climate, soil, geologi- 

 cal history and superficial characteristics, and, 



