TRISTAN DA CUNHA. 119 



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

 dilated on the other; 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 (Spheniscus), 

 should occur on the islands, since one species (S. Magellanicus), 

 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 from 

 their feet, forming a broad tract, leading to a lane in the tall 

 grass about a yard wide at the bottom, and quite bare, with a* 

 smoothly beaten black roadway ; this was the entrance to the 

 main street of this part of the " rookery," for so these penguin 

 establishments are called. 



Other smaller roads led at intervals into the rookery to the 

 nests near its border, but the main street was used by the 

 majority of birds. The birds took little notice of us, allowing 

 us to stand close by, and even to form ourselves into a group for 

 the photographer, in which they were included. 



This kind of penguin is called by the whalers and sealers 

 " rock-hopper," from its curious mode of progression. The birds 

 hop from rock to rock with both feet placed together, scarcely 

 ever missing their footing. When chased, they blunder and 

 fall amongst the stones, struggling their best to make off. 



With one of the Germans as guide, I entered the main street. 

 As soon as one was in it, the grass being above one's head, one 

 was as if in a maze, and could not see in the least where one 



* 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 Otaria Jubata. 



