91 
Mr Edmondston on the Arctic Gull, i^c. 
species of their respective countries ; and had the value of this 
principle been sufficiently appreciated, much erroneous, though 
ingenious, speculation might have been precluded. Influenced 
by this impression, I have occasionally had the honour of sub- 
mitting to the Society observations on some species of birds, of 
which the history and distinctions seemed not sufficiently ascer- 
tained ; and, on the present occasioil, I shall take the liberty of 
again trespassing, with similar views, on its attention. 
Although I am not aware of the circumstance, it is possible 
that some of the following remarks may have been anticipated 
by other ornithologists; but as they have been derived from 
long and personal observation of the birds to which they relate, 
in their native situations, and originally quite independently of 
books or museums, they may have their use, should this consist 
only in confirming the views of abler naturalists ; for facts are 
sometimes more valuable in their confirmation than discovery. 
1. Larus Parasiticus, or Arctic Gull. 
The first species I shall notice is the Larus parasiticus, or 
Arctic Gull, regarding which much diversity of opinion has 
existed ; some authors considering the white-breasted Ai’ctic 
gull as a species distinct from the brown, while others maintain 
it, with equal confidence, to be the male, the latter being the 
female, — that, therefore, the difference is merely that of sex. 
This opinion, however, I have unequivocally proved to be er- 
roneous, by careful dissection. Of four of the white-breasted 
birds, which I opened in Zetland, in the month of August last, 
one was most clearly a female full of eggs, the others were males ; 
of an equal number of the brown individuals, all were distinctly 
males ; and before this period I had met with several females in 
the same plumage. Their difference, then, as depending on sex, 
is disposed of. It must therefore be considered as connected 
either with difference of species, or progressive changes of plum- 
age of the same species, for it is too general and regular to be 
referred to mere variety. 
In the size, general appearance, form, modes of life, habits 
of migration, and anatomical structure, these two birds perfect- 
ly coincide ; and this agreement has not, I believe, been mate- 
rially denied, even by those who contend for their distinction. 
In what, then, can they differ, except in plumage Yet I 
