102 INACCESSIBLE ISLAND. 



there is a sort of mutual-benefit-alliance between the penguins 

 and the tussock. The millions of penguins sheltering and 

 nesting amongst the grass saturate the soil on which it grows 

 with the strongest manure, and the grass thus stimulated grows 

 high and thick, and shelters the birds from wind, rain, and 

 enemies, such as the predatory gulls. 



On the beach were to be seen various groups of penguins, 

 either coming from or going to the sea. There is only one 

 species of penguin in the Tristan group ; this is, Eudyptes 

 saltator, or the "well diving jumper " The birds stand about 

 a foot and a half high ; they are covered, as are all penguins, 

 with a thick coating of close set feathers, like the grebe's 

 feathers that muffs are made of. They are slate grey on the 

 Ijack and head, snow white on the whole front, and from the 

 sides of the head projects backwards on each side a tuft of 

 sulphur yellow plumes. The tufts lie close to the head when 

 the bird is swimming or diving, but they are erected when it is 

 on shore, and seem then almost by their varied posture to be 

 used in the expression of emotions, such as inquisitiveness and 

 anger. 



The bill of the penguin is bright red, and very strong and 

 sharp at the point, as our legs testified before the day was 

 over ; the iris is also red. The penguin's iris is remarkably 

 sensitive to light. When one of the birds was standing in our 

 "work room" on board the ship with one side of its head 

 turned towards the port, and the other away from the light, the 

 pupil on the one side was contracted almost to a speck, whilst 

 the other was widely dilated ; Captain Carmichael observed the 

 same fact.* The birds are subject to great variations in the 

 amount of light they use for vision, since they feed at sea at 

 night as well as in the day time. 



It seems remarkable that there should be only one species 

 of penguin at the Tristan da Cunha group, since in most 

 localities several species occur together. It would have seemed 

 probable that a species of "jackass" penguin {Sphenisciis) 

 should occur on the islands, since one species {S. Alagellanicus), 

 occurs at the Falkland Islands and Fuegia, and another {S. 

 demersus), at the Cape of Good Hope, intermediate between 

 which two points Tristan da Cunha lies. The connection 

 between these two widely separated Sphenisci is wanting ; it 

 perhaps once existed at Tristan, and has perished. 



Most of the droves of penguins made for one landing-place, 

 where the beach surface was covered with a coating of dirt 



* In the " Supplement to the British Museum Catalogue of Seals and 

 Whales, ' p. 7, reference is made to a like peculiarity of the iris in the 

 case of Otaiia jitbala. 



