266 
POPULAR SCIENCE REVIEW . 
In the case of the British Islands, there are other conditions 
besides breaks of geographical continuity which hinder the 
spread of some species. The unfavourable climate of the 
northern and western portions is probably one cause of the 
restricted range of many species, and their total absence from 
Scotland, Ireland, and in many cases, even from the north or 
west of England. Nothing strikes a naturalist, accustomed to 
the comparative abundance of insect life, even in the south of 
England, than its usual scantiness in Ireland, although the 
latter country probably possesses about two-thirds of our English 
species. 
The Mediterranean subregion presents us with several in- 
teresting problems, in addition to some previously mentioned. 
During the time that Spain and Italy have been separated from 
North Africa, great changes have occurred in the insects of the 
opposite coasts, as well as in the larger animals which now in- 
habit those countries. Oberthur, in his recently published work 
on the Lepidoptera of Algeria, doubts if any Algerian species 
of Zygcena is identical with any European species. This, how- 
ever, might perhaps be expected, for the genus Zygcena con- 
sists of a great number of closely allied and highly variable 
species which have their head-quarters in the Mediterranean 
subregion; and while some groups of animals (as many 
Mollusca) may remain almost unchanged for entire geological 
periods, yet others, which, like the species of Zygoma , are 
specifically unstable, may become modified very rapidly. But, 
notwithstanding the large amount of specialty in the Algerian 
insect-fauna, it is essentially the same as the European, and the 
African element is exceedingly small. (There are some species 
of insects confined to South Spain and South Russia. These are 
probably very ancient forms, and may even be relics of the 
preglacial Palaearctic insect-fauna.) The large mammals of 
Algeria are apparently nearly all of African origin, having 
crossed from the south after the Glacial Epoch, and subse- 
quently to the disappearance of the Saharan sea, and to the final 
separation of Europe and Africa, although some identical species 
of wide range penetrated into, or perhaps returned to Europe 
through Asia Minor, such, for instance, as the lion. 
The Ethiopian Region, or Africa, is at the present day chiefly 
remarkable for the great number of large mammalia which 
inhabit it. Many of these, though formerly abundant in 
Europe and India, have long disappeared from both countries ; 
and Africa has now a highly specialized character of its own. 
The Malagasy subregion, including Madagascar and the ad- 
jacent islands, is peculiarly remarkable, and t£ appears to indi- 
cate a very ancient connection with the southern portion of 
Africa, before the apes, ungulates, and felines had entered it ” 
