8 HUTTON, Penguins. \_lT^\y 



suggest no use for the feathers on the bill of Pygoscelis, nor 

 for the longitudinal grooves at the base of the mandibles in 

 SpJieniscus. The tail in Eudyptula^ Spheniscus, Megadyptes, and 

 Aptenodytes is short and composed of from i6 to 20 feathers ; 

 in Pygoscelis and CatarrJiactes it is long, and composed of 12 to 

 16 feathers. Of what use can these differences be ? Penguins 

 may perhaps use their tails as rudders, but it is difficult to say 

 which of these different tails would answer the purpose best. 



We must remember that different genera of Penguins some- 

 times inhabit the same island — as at Kerguelen, the F'alklands, 

 and Macquarie Islands. They seem to have the same food and 

 the same methods of capturing it. Genera which inhabit similar 

 localities when breeding, and which feed together, so far as we 

 know, on the same kind of food, could not have been differ- 

 entiated by the direct action of external conditions, and yet we 

 find it equally hard to explain how this could have been brought 

 about by natural selection. 



The specific characters are chiefly the differences in the colour 

 of the plumage or of the eyes, and some of these characters are 

 probably due to that part of sexual selection which I have called 

 preferential selection. The long plumes of C. chrysocoi)?e and the 

 yellow bands on the King and Emperor Penguins may be thus 

 accounted for, while the differences in the species of Spheniscus 

 may possibly be recognition marks. But there are some excep- 

 tions. The black throat of four different species of Catarrhactes 

 and two o{ Pygoscelis cannot be due to sexual selection, because 

 we cannot suppose that six different species belonging to two 

 different genera all wished to change their white throats into 

 black ones at the same time. This seems to be due simply to 

 reversion ; but it is a very interesting case. It is possible that 

 the red eyes of C. cJirysocovie may be a recognition mark to dis- 

 tinguish it from the brown-eyed C. pacJiyrJiyncJius. I can 

 imagine it possible that the earliest members of C. chrysocome 

 were driven from the rookery on account of their red eyes, and 

 in this way they may have been forced to keep together ; but it 

 does not seem likely that the white marks on the wings of 

 C. sclateri and E. albosignata are recognition marks, for they 

 breed in different localities from C, pachyrJiynchns and E. viinor, 

 from which they were derived. 



The effects of isolation are not so well marked in the Pen- 

 guins as in most birds, owing, probably, to their wandering 

 habits and to the difficulty they must experience in returning 

 after a long voyage to the place from which they started. Still 

 we find that C. scJilegeli, C. pacJiyrhy}icJuis, C. sclateri, E. albo- 

 signata, and the four species of Sphenisc7ts all inhabit separate 

 localities. We should expect that C. c/irysoconie, being so widely 

 spread, would show more decided variation than it does. Differ- 

 ences, however, do exist. Mr. Watson has shown that the skull 



