158 THE AMERICAN NATURALIST. [Vor. XXXVI. 
by supposed changes in the conditions of life that have taken place 
during the earth’s history. 
The investigation of instances of the latter kind forms a large 
part in Jacobi’s paper, and he has collected valuable material which 
tends to show that certain parts of the earth’s surface, in their fauna 
and flora, possess a uniformity which is inexplicable by the present 
conditions. He calls those parts “areas of dispersal” (Ausérei- 
tungsgebiete) and indicates them on his map (Pl. VII). There are 
fifteen of them : 
Arabian. 11. Philippinian. 
1. Greenlandian. 6. 
2. Lusitanian. 7. Indo-African. 12. Southern Japanese. 
3. Mediterranean. 8. Antarctic. 13. Siberian. 
4. Sarmatian. 9. Papuan. 14. Beringian. 
5. Iranian. to. Farther Indian. 15. Central-American. 
Of these, the 4th (southern Russia and Turkestan), the 5th 
(Persia), the roth (Farther India), and the rsth (Central America) 
are situated on continents and do not present any remarkable 
features, since they are not opposed to the present conditions. 
The 2d, connecting England with western France and Spain, the 
3d, connecting the Mediterranean countries, the gth, connecting 
New Guinea with Australia, the 11th, connecting the Philippine 
Islands with each other and with Formosa, the 12th, connecting 
South Japan with Korea and China, the 13th, connecting North 
Japan with Siberia, and the 14th, connecting Siberia and Alaska, 
are well known and have been generally accepted as well established. 
The chief interest centers in the remaining areas of dispersal, 
namely, the rst (connection of East Greenland with Spitzbergen, 
Norway, and Scotland), the 6th and 7th (connection of East Africa 
and India, partly by way of Abyssinia and Arabia, partly by way 
of Madagascar and the islands of the Indian Ocean), and the 8th 
(connection of South Africa, Australia, New Zealand, and South 
America with Antarctica). Indeed, none of these connections is 
new to science, and some of them have been repeatedly discussed 
lately, but it is interesting that Jacobi's studies have led him also 
to the assumption of the former existence of these very important 
biogeographical relations, which can only be explained by the theory 
of a former connection of the respective parts by land. In the dem- 
onstration that such conditions must have existed in former times, 
and in the collection of known facts as well as introduction of new 
ones, which tend to support this assumption, lies the chief value of 
