SYRINX OF PENGUINS. 



15 



however, have a somewhat greater circumference ; and this is specially noticeable in 

 the last. But the bronchial semi-rings 2-4 have a very wide span, so that the windpipe 

 in this region reaches its greatest dorso-ventral width ; from the fourth bronchial 

 semi-ring backwards the circumference of the .bronchus decreases rapidly. Only the 

 first bronchial ring is complete to its inner rim is attached the upper end of the 

 membrana tympaniformis. The intrinsic muscles terminate in the middle of the ante- 

 penultimate ring, while the extrinsic muscle leaves the trachea at about the twentieth 

 ring from the syrinx, counting from the last tracheal ring forwards. The trachea of this 

 species shares with that of the remaining penguins the peculiarity of a median septum 

 which extends the whole length of the trachea, from the syrinx forwards as far as the 

 upper third of the tracheal tube. This 

 septum is made up, in the adult, of a 

 number of bony bars corresponding 

 numerically to the number of the tracheal 

 rings (Fig. 5) ; while that of the nestling 

 differs from that of the adult only in 

 being, like the rest of the trachea, entirely 

 cartilaginous. 



VI. SOME FACTS CONCERNING THE 

 EMBRYO AND NESTLINGS. 



I PROPOSE to deal here with a few facts 

 concerning the rhamphotheca and the ex- 

 ternal nares, the palate, the developing 

 wing and the tarso-metatarsus. 



P1O. 5. THE SYRINX OP AN ADULT EMPEROR PENGUIN, SIDE 

 VIEW, AND IN SECTION TO SHOW THE TKACHEAL SEPTUM. 



B = bronchidesimus ; br. = bronchus ; s. = septum ; 

 tr. = trachea ; t. = trachealis muscle ; tm. = tympanic 

 membrane. 



I. = 1st tracheal ring; I. 1 = 1st bronchial ring; 

 II. = 2nd bronchial ring. 



Tlie Rhamphotheca. 



The shape of the beak in the embryo 

 Emperor Penguin, at the time when the 



feather papillae are just making their appearance, differs from that of the nestling, just 

 as markedly as the beak of the latter differs from that of the adult. 



In the embryo at the age just indicated the beak is relatively long, cylindrical, 

 slightly swollen at the tip, and shows no trace of the egg-tooth. The anterior nares are 

 open, but there is no sign of separate rhamphothecal plates, or of the groove which later 

 appears in front of the nostrils. 



In the newly-hatched nestling the culmen of the beak is arched, while near the tip 

 is a small egg-tooth, which is apparently absorbed, since it is not detachable as in, say, 

 young gallinaceous birds. Here, again, there is no trace of separate elements in the 

 beak sheath, such as are met with in the petrels for instance, but there is a deep groove 

 running from the uares forward, nearer the tomium than the culmen, but this does not 



