138 THE FOWLER IN IRELAND. 



its lower edge, and lying between its lower and 

 middle third. When a bristle is introduced into the 

 slit, it never succeeds in forcing a passage into the 

 nasal cavity. If the skin which forms the outer 

 boundary of the slit is carefully reflexed, a groove is 

 exposed which runs from the external slit-like nostril 

 to a narrow canal, lined apparently by modified 

 mucous membrane. This canal, when the mucous 

 membrane remains, is externally from i^ to 2 millim. 

 in diameter ; but it rapidly diminishes, and appears 

 to end blindly. In all the specimens examined, 

 however, when the skin has been reflexed, it is pos- 

 sible to pass through this canal, without forming a 

 false passage, a bristle about the size of an ordinary 

 horse-hair i.e., less than i millim. in diameter. 

 The bristle is more easily passed in young birds 

 than in old ones : this seems to be due to the 

 osseous canal being relatively larger than in the 

 former. Almost immediately beyond this narrow 

 passage is the large nasal chamber, lying above and 

 internal to the palatine bone, and in free communi- 

 cation with the buccal cavity. The mucous mem- 

 brane lining the nasal chamber has the same struc- 

 ture and the same nerve-supply as in other aquatic 

 birds. The nasal region of the Cormorant, and to 

 some extent also of the Gannet (Sula), thus differs 

 chiefly from the nasal arrangement in other birds 

 (i), in having a very small external nostril, the 

 passage in this slit-like aperture being almost 

 obliterated ; (2), in having the osseous canal only 

 i^ to 2 millim. in diameter externally, and scarcely 

 i^ millim. at its narrowest part ; and (3), in having 

 the nasal chamber in very free communication with 



