^74 Dr Fleming on tlie CJuxnges of Colour in the 
reversed. Hence it follows, that in those animals in which a 
change of colour takes place, without a change of covering, the 
winter dress will always be found pale or white coloured, while 
the summer dress will be bright or dark. There is one remark, 
however, made by Captain Sabine, while treating of the Larus 
glaucus, which appears to militate against this law : “ In win- 
ter, the mature bird has the head and neck mottled with brown, 
as is usual with all the white-headed gulls. In the perfect 
summer state, the whole plumage is white, excepting the ba:ck, 
scapulars, and wing-coverts, which are a very light ash colour,” 
p. 544. But as the observations w’hich led to this remark were 
made on stuffed specimens, it is possible that neither the age of 
the individuals, nor the periods at which they were shot, ha,ve 
been accurately recorded. In a domesticated state, Montagu 
observed the heads of the Larus canus and fuscus become mot- 
tled during the winter season, and resume their white state in 
the spring ; but it remains to be determined if similar changes 
are effected in a wild state, where the quantity of food and the 
shelter are so very different. The scepticism which we are here 
disposed to entertain, is sanctioned by the observations of ten' 
years attention to the subject, and even by numerous remarks, 
which occur in various other parts of the paper. We trust that 
Captain Sabine will not censure our caution as originating in ^ 
regard for a favourite hypothesis, since we can assure him, that 
the discovery of truth is our only object, and that the value 
of our conclusions is estimated by the strength of the proofs by 
which they are supported 
* We are disposed to request much stronger evidence than opinioju, in the ab- 
sence of any direct proof or analogy, before we admit that the black markings of the 
primary quill-feathers of the herring-gull, which endure the severities of a Europe- 
an winter, vanish altogether as the effect of climate in the summer of Greenland. 
Yet Captain Sabine, on the authority of Mr Temminck, regards the Silvery gull 
with white primary quill-feathers, as the mature Greenland summer dress, and the 
mature Europeau winter dress, of the Herring-gull- If this is really the true state of 
the case, we would ask. What is the mature European summer dress of the Larus 
glaucus ? Has it ever been found with black markings on the primary quill-feathers ? 
This last species of gull is alluded to by Captain Sabine as a British bird. In the 
spring of 1818, Mr Bullock, whose valuable additions to the list of British birds 
are well known, shewed me a specimen of one which he had obtained from Zet- 
land, and informed me that others had be6n shot at the mouth of the Thames and 
