536 THE GANNET 



attention has been drawn by Mr. Maynard (^.c, p. IIG), 

 and which is clearly shown by Mr. Wilson in his drawing, 

 made from a fresh subject. Mr. Maynard thinks that 

 the tongue of a Gannet is probably retractable, the hyoid 

 bones being long, and surrounded with muscles.* 



The Eyes. — The eye-ball of a Gannet is larger than 

 the eye-lid aperture would lead us to expect. That 

 which may be called the external eye has a circumference 

 of 3.2 inches, and its position is remarkable. It is so 

 set in the head as to look forwards, and forwards only ; 

 accordingly the Gannet, unlike most birds, can see an 

 object with both eyes at once.f 



But this is only true of an adult Gannet, for in a young 

 one, six months old or so, the supra-occipital bone has 

 not yet acquired its ultimate shape. Nevertheless young 

 Gannets commence plunging early {see p. 403), in fact, 

 before they are four months old, at which age they could 

 not see a fish with both eyes simultaneously. 



* In the Darter (Plotus) the tongue is practicallj' obsolete (see illustra- 

 tion in Beddard's " Structure and Classification of Birds," p. 20). In 

 Pelecanus it is even more raised than in Sula, but scarcely any larger, 

 c/. Nitzsch-Giebel, "Die Zunge des Vogel." 



t The position of a Gannet's eyes is not dissimilar to that of Owls, 

 which drop on their prey, but not head foremost. Terns and King- 

 fishers, however, which are plunging birds, and dive into the water 

 from a height very like a Gannet, have their eyes located on the sides of 

 the head. 



