The genus _Larus_ (Gull) of the early writers included many birds now separated from it--the Skuas, or parasitic gulls; Lestris; the Terns, or sea-swallows; Sterna; and some others--the consequence of increasing knowledge in natural science being the gradual limitation of genera by the use of more precise and restricted characters. All these genera now form part of the family of Laridæ, or gull-like birds--the system of grouping together those genera which exhibit striking analogies in plumage or habits securing the advantages of a natural arrangement, without the danger of that confusion which so often results from loosely defined genera. The tendency is indeed to still further subdivision--the kittiwake (_Larus rissa_) having been made the type of a new genus, Rissa (Stephens), and the blackheaded gulls classed together as the genus _Xema_ (Boië)--the periodic change of the colour of their heads from the white of winter to the black of summer, their more rapid and tern or swallow-like flight, and their inland habits, forming so many striking and apparently natural marks of distinction. To this genus, if finally admitted, will belong the Little Gull (_Xema minuta_). The term _Larus_ is adopted from the Greek, the ancient Latin name as used by Pliny being _Gavia_. Brisson (1763) applies _Larus_ to some of the larger species, and _Gavia_ to a multitude of others; but there is much confusion in his identifications of species, and the line of separation was not well considered. Modern writers also subdivide the gulls, for the sake of convenience, into two sections--the larger, or those varying from nineteen to twenty-six or more inches in length, the “Goelands” of Temminck; and the smaller, or “Mouettes” of Temminck. But this system of division is imperfect, as it veils the remarkable relation existing between many of the larger and smaller gulls, which should not therefore be separated from each other. This relation was noticed by some of the earlier writers. Willoughby designates under the name _Larus cinereus maximus_ both the herring and the lesser blackbacked gulls; and under that of _Larus cinereus minor_, the common sea-gull. This kind of relation is indeed strikingly displayed amongst British gulls--as in the greater and lesser blackbacked gulls, the Glaucous and Iceland gulls, the herring and common gulls, and, we may add, the blackheaded and little gulls; and it is very probable that further research will show that it exists still more widely.