238 Canou Tristram on the Polar Origin of Life 



change^ certainly not during geological history ; while at the 

 same time they admit the possibility of stupendous land- 

 changes having taken place. in the earlier age of the planet, 

 of which we can find no existing evidence. 



It is unnecessary to enter on the geologic record of the 

 sequence of the Arctic flora from the Silurian corals to the 

 later Miocene; this has been admirably summarized by 

 Lt.-Col. Feilden in his Presidential Address to the Norfolk 

 Naturalists' Society in 1886. Ornithology cannot afford the 

 like geological evidence with botany, for we know how com- 

 paratively rare are ornithic relics. We are therefore in tliis 

 branch of biology more exclusively dependent on the evidence 

 afforded by the distribution of existing forms. 



If we can trace a gradual development from the generalized 

 to the more specialized forms only in passing from north to 

 south, from the North Pole by the great circles of longitude — 

 while if we pass by the circles of latitude round the world 

 we find, until we come to the confines of the arctic zone, 

 that the former are specifically unlike while the climatic con- 

 ditions are the same — we have the locality of origin clearly 

 indicated. The moment we reach the Arctic zone we are 

 everywhere surrounded by the same species. But if we follow 

 the continental masses of the New World to the South Pole, 

 thence returning up a meridian which crosses Africa and 

 Europe, or Australia and Asia, we shall find in the descent 

 abundant fossil evidence that we are moving onwards by the 

 path along which the prehistoric migrations of the animal- 

 world proceeded, and on our return we shall find that we are 

 movino- counter to their obvious movement. 



Round the shores of the Arctic Sea the same fauna and 

 flora are found in every meridian. As we pass southward 

 alou"- the three principal lines of land towards the Capo, 

 Tasmania, and Tierra del Fuego, specific identity gives place 

 to mere identity of genera; these are replaced by family 

 resemblances, and at last even the families become in a great 

 measure distinct, not only on the great continents, but also 

 on the islands, till every little rock in the Southern Ocean has 

 its peculiar inhabitants. Thus the living faunas of Patagonia, 



