NATCH ATI VE OF THE CRUISE. H03 



includes, according to ornithologists, the two .separate species Ehsdyptes chrytocome and 

 Eudyptea okrysolophug, along with others which I have not had an opportunity of examin- 

 ing. Of these Eudyptes chrysocome has much the more extensive geographical range, 

 being met with as far north as the Island of Tristan da Cunha, whence it extends south- 

 ward to Iverguelen Island. Eudyptes chrysolojihus inhabits Kerguelen Island, whence it 

 extends southward to the islands of the Antarctic. 1 The genus Aptenodytes (including 

 Pygosceles) has a wide geographical range in the southern hemisphere, extending from 

 the Falkland Islands to the islands of the Antarctic Ocean. The limitation of the geo- 

 graphical range of the group to the southern hemisphere is not a little remarkable, 

 and so far as I am aware no expla nation of the fact has hitherto been offered. 



" That it does not depend on temperature alone seems probable from the fact that they 

 are met with from the equator southwards to the Antarctic Ocean. At the same time, 

 it is interesting to observe that Penguins reach the equator only on the coasts of Chili 

 and Peru. Along these coasts the cold Peruvian Current from the Antarctic Ocean 

 carries a low temperature northward as far as the Galapagos Islands. This current, as 

 shown by the position on the map of the isocheimal or cold water line, extends from 

 the Antarctic Ocean along the west coast of South America, and has a surface tempera- 

 ture at the equator of from G2° to 68°, whereas elsewhere the equatorial region of the 

 Pacific Ocean has a temperature varying from 81° to 88°. Now, it will be observed that 

 the most northern geographical limit of the Penguins corresponds with that of this cold 

 Peruvian Current, and it seems not improbable that while temperature does not directly 

 affect the distribution of these birds, it may do so indirectly, inasmuch as this cold 

 current passing from the pole to the equator will facilitate the passage northward of 

 those cold water organisms which, inhabiting the Antarctic Ocean, constitute the food 

 of the Penguins. The home of the Penguins is undoubtedly in the cold regions of the 

 Antarctic, but their food supply being carried northward by means of the cold Peruvian 

 Current, the area of distribution of the Spheniscidse has been correspondingly extended, 

 and now reaches from the Antarctic Ocean to the equator. 



" The fact that the Challenger officers seldom noticed these birds more than 40 or 50 

 miles from land 2 or ice, seems to show that having once adopted a residence, they are 

 very far from being addicted to those migratory habits which their peculiar structure and 

 mode of life seem so well adapted to encourage. 



" With regard to the distribution in time of the Spheniscidse, we know very little 

 at present, our knowledge of fossil forms being limited to a humerus, coracoid. and tarso- 

 metatarsal bone, which were discovered in the Eocene formation of New Zealand. 3 The 

 metatarsal bone has been described by Professor Huxley, 4 who established the genus 



1 Gray, Handlist of the Genera and Species of Birds, part iii. p. 98, 1871. 

 * Solater, Zool. Chall. Exp., part. viii. p. 132, 1880. 



3 Hector, J., Trans. New Zealand Inst., vol. v. p. 4:!8, 1872. 



4 Quart. Joum, Geol. Soc, vol. xv. p. 670, 1859. 



