238 THE VOYAGE OF H.M.S. CHALLENGER. 



respect of their habits most nearly resemble them. From the observations of 

 Tegetmeier^ it would appear that in diving the movements of the Penguins under water 

 are accomplished solely by the use of the wings, the legs being extended behind the 

 bird, just as they are during flight, and taking no part in the propulsion of the bird through 

 the water. It thus appears that the posterior extremities of the Penguins act chiefly as 

 organs of progression when the bird is on land or when swimming on the surface of the 

 water, but that when diving the legs take no part in the locomotion of the bird, which 

 under these cii'cumstances becomes truly a subaqueous flight. 



The geographical distribution of the Spheniscidas is of interest." The various members 

 of the group are entirely confined to the southern hemisi)here, not one single species of 

 Penguin being found north of the equator. In the southern hemisphere, however, their 

 distribution is very extensive, reaching from the Gallapagos Islands on the equator south- 

 wards to the Antarctic Islands. Of the various species of Penguin referred to in the pre- 

 ceding pages, Spheniscus demersus is confined to the vicinity of the Cape of Good Hope, 

 Spheniscus Qmigellanicus to that of Cape Horn, Sp>hemscus mendiculus to the coast of 

 Chili, while Spheniscus minor inhabits the South Pacific, in the neighbourhood of 

 'Australia and New Zealand. The genus Eudijptes includes, according to ornithologists, 

 along with others which I have not had an opportunity of examining, the two separate 

 species Eudyptes ckrysocome and Eudyptes chrysolophus. Of these Eudyptes chrysocome 

 has much the more extensive geographical range, being met with as far north as the island 

 of Tristan d'Acunha, whence it extends southwards to Kerguelen Island. Eudyptes 

 chrysolophus inhabits the island of Kerguelen, whence it extends southwards to the 

 islands of the Antarctic.^ The genus AiMnodytes (including Pygosceles) has a wide 

 geographical range, extending from the Falkland Islands in the north, to the islands of the 

 Antarctic Sea in the south. 



The limitation of the geographical range of the group of Spheniscidse to the 

 southern hemisphere is not a little remarkable, and so far as I am aware no explanation 

 of the fact has hitherto been oflered. That it does not depend on temperature is evident 

 from the fact that they are met with from the equator southwards to the Antarctic Ocean.* 

 It appears not improbable that it may depend on the relative abundance of the food 

 supply (cephalopods and Crustacea) found in the southern and northern hemispheres 

 respectively. 



1 Diving Birds in the Zoological Garden, Tlie Field, April 28, 1883, p. 563. 



' Wallace, Geographical Distribution of Animals, vol. ii. p. 366. 



' Gray, Handlist of the Genera and Species of Birds, part iii. p. 90. 



* With reference to this matter, I have been favoured with the following interesting remarks by the editor of the 

 Challenger Reports. " The Penguins reach the equator only on the coast of Chili and Peru. Now the Peruvian current 

 from the antarctic skirts along this coast, and takes a low temperature as far north as the Gallapagos Isles, — the tem- 

 perature of the sea being tliere (equator) 62^ to 66°, while in the middle of the Pacific (equator) the surface temperatuie 

 is 81° to 88°. Temperature, therefore, most probably has something to do ■nith the limitation of the geograjjhicul 

 distribution of the Spheniscidse." 



I 



