226 Mr. H. Seebohm on the Genus Himantopus. 
tion is broken. I propose to approach the subject from quite 
a different point of view. 
A careful study of the geographical distribution of the 
couple of hundred species and subspecies of birds which com¬ 
pose the family Charadriidse leads to the conclusion that 
they are the variously modified descendants of a species of 
wader which lived on the shores of the north polar basin 
some time before the close of the Glacial epoch. During 
one of the later Glacial periods this circumpolar species was 
driven south, and split up into parties, which were isolated 
in various parts of the tropical and subtropical regions, and 
became, during the period of their isolation, differentiated 
into species. These species were the ancestors of the present 
genera of Charadriidse, and during the interglacial period 
which followed their differentiation (probably the last of the 
half dozen or so which occurred) most of them followed the 
retreating cold and became (with few exceptions) once more 
circumpolar ; but instead of being, as they formerly were, 
of one species, they then consisted of a dozen or more well- 
defined species, from one of which no doubt the genus Hi¬ 
mantopus descended. During the last Glacial period the 
dozen or more species were again dispersed, each of them was 
split up into parties, which becoming isolated from each other 
were differentiated into the now existing species. 
Let us endeavour to trace the history of the ancestral 
species from which the ten species now forming the genus 
Himantopus are descended, and let us try to follow its emi¬ 
gration, from the period when it consisted of only one species 
living on the shores of the north polar sea, down to the pre¬ 
sent time when its descendants have become ten species 
scattered over the greater part of the globe. 
Probably the first split in the circle of circumpolar birds 
was the intervention of a glacier, stretching from the north 
pole down the mountains of Greenland. The semi-isolation 
caused by the stoppage of any interbreeding between the 
birds of the Atlantic coast of America and that of Europe 
must naturally have produced a differentiation between the 
birds of Grinneil Land and Scandinavia, and there is reason 
