Letters, Extracts from Correspondence, Notices, S^c. 231 



M. Bolle rests his arguments in favour of establishing a new 

 species, firstly, on some supposed peculiarity of colour. After 

 having given a description of his bird, he adds, " II reste a remar- 

 quer qu'autant queje me rappelle [the italics are mine], il n'offre 

 point de grandes variations suivant la saison ou suivant le sexe, 

 et qu^en aucun temps il no presente la plus legere trace de vert." 

 Now this is rather indefinite language for any one attempting 

 to establish a distinct species — a matter in which the conscience 

 of an ornithologist should be particularly tender, when it is 

 considered what confusion has been induced by a too great 

 readiness in authors to stand sponsors to species which could 

 readily dispense with their well-meant ofiices. 



As an illustration, I might take the Columha trocas, which is 

 described by Dr. Heineken in ' Brewster's Journal ' as a new 

 species, though it is doubtless identical with the Columha lauri- 

 vora of Webb and Berthelot. Montagu fell into a like error in 

 the case of his Alauda trivialis, which is no more than our old 

 friend the Anthus pratensis after its autumnal moult. 



M. Bolle does not enter into any particular description of the 

 young bird of the year of his assumed species, nor does he tell 

 us whether he has noted at what season of the year his speci« 

 mens were obtained. All he tells us is that he has made a 

 careful examination of several skins which he brought from the 

 Canary Islands, and instituted a comparison, which he says had 

 hitherto been neglected, between these skins and those of the 

 true Pipit. 



Secondly, M. Bolle urges that the size of his bird is smaller 

 than that of the A. prateyisis, and that the relative length of the 

 claw in his specimen- is greater. 



I am quite aware of the difficulty of giving accurate descrip- 

 tions of birds, and of the danger of trusting too implicitly to 

 measurements if you have only prepared skins to rely upon ; 

 for, in spite of the greatest care, colours will fade, and skins will 

 shrink, if, indeed, they have not been stretched or displaced in 

 the process of preparing them. This led to my taking very 

 accurate descriptions and measurements of birds in the flesh, in 

 Madeira, in the year 1851. I append a description thus taken 

 of the A. pratensis. In the summer of the same year I brought 



