1899] THE HABITS OF THE NORTHERN FUR SEAL 19 
cutter “Rush”), and October 4 to 22 on St. George Island, thus 
missing only the earlier part of the season of 1896. In order to 
complete my knowledge, and to be able to observe the seals in the earlier 
part of the breeding-season, I reached Bering’s Island in 1897, on 
June 19, and remained there until August 2, when I sailed for Copper 
Island, and landed there on the following day. On August 19 I left 
Copper Island in an unsuccessful search for seal rookeries on the 
Kamchatkan coast, and did not again return to the seal islands. Dur- 
ing my stay on the islands I personally examined and walked over 
the whole extent of all the rookeries, with the exception only of one 
or two of the lesser ones on the Commander Islands, which I had 
to be content to observe through my binoculars, either because they 
are inaccessible from the land side, or because I had not permission to 
approach them more nearly. 
Enumeration of Seal Islands. 
The islands whither the seals resort for breeding purposes are now 
all well known, and it is unlikely that the most diligent search can 
add to their number. They are the Commander and Pribilof Islands 
in Bering’s Sea, certain of the more Northern Kuril Islands,’ Robben 
Island (in the Sea of Okhotsk), and possibly one or two other small 
rocks” and islets in the same sea. It can hardly be doubted that the 
presence of the seals on these islands, apparently scattered at random 
throughout the North Pacific, and their absence from many others 
equally suitable for their purpose, such as the Aleutians, depends 
entirely on the former presence or absence thereon of man. The Com- 
manders and Pribilofs are the only large uninhabited islands in the 
North Pacific, and there are no rookeries on the Aleutian Islands, 
which, although affording very suitable conditions, are inhabited through- 
out their extent. 
What Guides the Seals in their Choice of an Island or Rookery. 
A glance at Sir John Murray’s map (Geographical Jowrnal, August 
1898) to illustrate the annual range of the surface temperature of 
the ocean will show that the question of temperature has had no very 
ereat influence on the choice of the seals of islands on which to bring 
up their young. Whereas the Pribilof and Commander Islands le in 
regions where the surface temperature is cold, and has an annual 
variation of only 20° F., the corresponding figure for the Northern Kuril 
Islands is 30°, while the little rookery at Robben Island lies close to 
the border line of regions where the annual variation amounts to 35° 
and 40° F. respectively. Again, whereas in the event of a backward 
1 Shnednoi, Raikoke, and Mushir. 
2 St. Iona and the Shantai Islands. 
