1905 - 6 .] Gollembola from the South Orkney Islands. 479 
Land, together with the presence of the Isotoina on Kerguelen, 
point to the former existence of extensive land tracts south of the 
American continent, with connection, either by way of Antarctica 
or of South Africa, to Kerguelen. It cannot indeed be inferred 
from the distribution of these springtails that there was at any 
one period a continuous land surface from Patagonia and Graham 
Land to Kerguelen. But it can hardly be denied that the insects 
must have travelled overland, though the land connections may 
have varied in extent, and become broken at different points 
during different periods. The bathymetrical work of the Scotia 
Expedition, as set forth by Bruce (1905), demonstrating a con- 
tinuous bank, less than 2000 fathoms beneath the surface of the 
South Atlantic, stretching eastwards from the South Orkneys 
towards South-East Africa, makes the former existence of one such 
land-tract the more credible. And the geological structure of the 
South Orkneys leaves no doubt that they must be regarded as 
strictly “ continental ” islands. Similarly, the “Kerguelen 
plateau,” as mapped by the explorers of the Valdivia (Schott, 
1902), renders in the highest degree probable the former union of 
Kerguelen with Antarctica ; and a connection thence to South 
Africa is not impossible of acceptance. 
If, as we believe, these springtails — apparently members of a 
typically Antarctic fauna — owe their presence on the islands 
that they now inhabit to a former extension of the Antarctic 
continent, they must be of a considerable geological age. Ort- 
mann (1904) considers that the greatest extension of Antarctica 
existed in the Cretaceous and Eocene eras. Hutton (1905) argues 
for the Jurassic as the period of most extensive land in southern 
regions. We may safely conclude that Cryptopygus and Isotoma 
octo-ocidata have survived throughout the Tertiary epoch at least, 
with comparatively little change of structure. 
The affinities of Isotoma Brucei open up a problem of even 
greater interest. It is closely allied, as we have seen, to I. 
Beselsii , a springtail which has been found in Spitzbergen, Jan 
Mayen Island, Scotland (shores of the Firth of Forth), Greenland 
(Polaris Bay), and Massachusetts. We cannot doubt that this 
affinity points to a former connection between the Antarctic 
continent, of which the South Orkneys once formed part, and the 
