EVOLUTION OF PENGUINS. 27 



the sheath of the upper jaw in the puffin (Fratercula arctica), or in the moult of the 

 claws in grouse. 



Some day another Antarctic Expedition will be sent out, when it is to be hoped 

 that, so far as the penguins are concerned, special efforts will be made to secure the 

 earlier nestling stages of the King, and the latter stages of the Emperor Penguin 

 full-grown nestlings of the latter being especially needed ; while of both species the 

 early and middle embryonic stages are wanted. Ripe embryos will add but little of 

 real value to our knowledge, since they differ but little of course from the newly- 

 hatched nestling, and furthermore, several examples are among the spoils of the 

 expedition herein concerned. A few adults of both species would certainly be useful 

 if preserved entire, in spirit, or in ice. 



Bearing in mind the temperature of the air in which these birds live, observations 

 on their breathing would be of value, since, as we have pointed out, the external nares 

 are closed ; thereby respiration has to be carried on by way of the mouth. This 

 being so, it is possible that observations may show that some mechanism 

 has been adopted whereby the air taken in at the mouth can be retained and warmed 

 before being passed on to the lungs. It may be that the tracheal septum, by increasing 

 the vascular surface of the interior of the trachea, may serve some such purpose. This 

 septum can, however, hardly have been developed to serve this special end, inasmuch 

 as it occurs in the embryos of all birds, and the adult of some other species which live 

 neither in a specially cold atmosphere nor have closed nares. 



REFERENCES. 



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P.Z.S., 1879. 



3. Beddard, F. E. " The Structure and Classification of Birds." London. 1898. 



4. Davies, H. R. " Beitrag zur. Entwickl. der Feder." Morph. Jahrb., xiv. (1888), xv. (1889). 



5. De Winton, W. E. " On the Moulting of the King Penguin." P.Z.S., 1898 and 1899. 



6. Gadow, H. " Bronn's Thier-reichs." Bd. vi. ; Abth. iv. : Vogel. Systemat. Theil. (1893). 



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