226 Mr. H. Seebohm on the Genus Himantopus. 



tion is broken. I propose to approach the subject from quite 

 a dififerent 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 

 cii'cumpolar ; 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 ^Yhich 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 Grinnell Land and Scandinavia, and there is reason 



