144 GREY-HE AUED YELLOW AVAGTAIL. 



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 

 difierence 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 



