144 
GREY-IIEADKD YELLOW WAGTAIL. 
constitute them species. The intermediate forms do not 
come under our observation so frequently, and we 
therefore lose the significance of the serial affinities. 
Believing, as I do, that much of the system of determining 
species in Natural History in modern days is deficient 
in sound scientific principle, I have no occasion to seek 
for a solution of the difficulty in the theory of trans- 
mutation. I think that differences of climate and food 
are all-sufficient to produce a great majority of the va- 
riations we meet with: and as it is more than probable 
that the world contains a vast number of special cases 
wherein these influences of food and climate operate 
distinctly, I have no difficulty in accounting for the 
variation of species, or of satisfying myself that the 
difference of a feather here or there is not sufficient to 
justify the splitting up of our naturally defined genera 
and families into an interminable long list of Greek 
derivatives, quite sufficient to frighten away nine tenths 
of the students of nature from the most beautiful and 
instructive of all pursuits. 
The Grey-headed Yellow Wagtail is a common bird 
during the summer in Italy and other hot parts of 
Europe, as Dalmatia, Tuscany, Sicily, Sardinia, and the 
south of France and Spain. This is its area, but it is 
also occasionally found in Belgium, and it has been 
taken by M. De Selys-Longchamps in the neighbourhood 
of Liege. It has also been found in Nubia and Egypt. 
Of its habits we have the following in the ‘^Oiseaux 
de la Belgique,” of M. Ch. F. Dubois: — 
‘‘The extensive plains, meadows, and marshes are the 
places which these birds more especially frequent; they 
like a moist soil among osiers and reeds, and other 
aquatic plants, especially the male, who in the breeding 
season will remain for hours in these retreats appealing 
