49.2 ]Mr. P. R. Lowe — Observations 



continental s^jecies and the equally remarkable amount of 

 variation in insular forms. In no point is this more obvious 

 than in the very slight amount of variation in the depth of 

 coloration of the grey throat-patch in continental species, 

 although they may be separated by thousands of miles. 

 As regards insular species^ there is probably no genus 

 in the world which is marked by such numerous island 

 forms presenting such striking and such very constant 

 specific differences ; and this in spite of the fact that on 

 most of the islands the local conditions are remarkably 

 similar. 



(4) The division which can be made of all the species, 

 whether continental or Antillean, into two well-defined 

 groups : — 



(a) With a definite white wing-spot. 



[b) Without any wing-spot, 



(5) The restriction of these two races to certain very 

 definite tracts or regions which are not scattered in a hap- 

 hazard way, but in each case are more or less continuous 

 and belong to certain definite and distinct geological 

 systems. 



Thus the distribution of the two races seems to faithfully 

 conform to or reflect what we know of the past geological 

 epochs of elevation or depression which have affected the 

 areas to which they are confined. A reference to the accom- 

 panying sketch-map (Plate VII.) will perhaps make our 

 point clearer. 



In this map the area of distribution of the race loiih wing- 

 spots is indicated by diagonal lines ; whereas that of the 

 race without iving-spots is indicated by a fine dot tint. To 

 accentuate the different origin of the two races, the inset 

 map representing South America only, is drawn so as to 

 picture in a rough way the distribution of land-areas in 

 early and middle Tertiary times. By this means the geo- 

 logical differentiation of the areas now inhabited by the two 

 races may be more easily realised at a glance. Confining, 

 then, for the moment our attention to the southern conti- 

 nent, we see that the white-wing- spotted race (represented 



