2 
ZOOLOGICAL LITERATURE. 
71° and 75 whilst in South-eastern Siberia, between lat. 52° 
and 62® N., 44 mammals, 157 birds, and 4 reptiles were collected. 
The following chapter is directed against the tendency of many 
zoologists to separate the slightest variations under distinct 
specific names. The identity of most of the Mammalia of the 
north of Asia and America becomes evident as soon as a sufficient 
number of examples from various localities are examined. The 
causes of variation must be manifold ; climate is certainly not 
the only cause. Thus, with regard to the variation of size, it has 
been observed that Asiatic examples are of greater size than 
European ; of many birds a smaller and a larger variety exist, but 
both are found in the same localities, the lesser variety being 
probably the product of a second brood. Mountain- races in 
Europe are generally the smaller; inSiberiathey are alarger than 
those of the plains. Food must be one of the principal causes of 
vigorous growth : where the animal finds a regular and plentiful 
supply, and where the food is enjoyed without disturbance, there 
races of larger growth will be produced. Variations of colour 
are likewise dependent on various causes. 
Passing on to the distribution of animals, the author expresses 
his belief that there is originally a continuity of distribution 
of every species; but it is frequently now found interrupted 
from geological changes, or in consequence of migration or of 
partial extinction. In Siberia the following animals are extinct, 
or exposed to the danger of becoming entirely or locally extinct: 
— Rhytina, Enhydris, Otaria stelleri and ursina, Ovis montanus, 
Beaver, Sable, Wild Cat, Wolf, Bear, Eland, and the Saiga 
Antelope. To prevent the extinction of useful animals it is ne- 
cessary to protect them by laws, as, for instance, in the case of the 
Sea-Bear, which decreased so rapidly in numbers that a Russian 
Company was obliged to introduce, in the year 1830, a system 
of preservation on the island of St. Paul. The consequence was 
that they were .enabled to kill 4000 animals in 1840, 8000 in 
1841, 12,000 in 1843, 15,000 in 1845, and 47,960 in 1861, the 
species being, moreover, compelled to resort to other additional 
localities for breeding. 
The circumpolar^* fauna is divided into hyperhoreaV* and 
circumboreal ** animals, the latter being subdivided into 
Tundra ** species, that is inhabitants of open country, and into 
/ore^Z-species. We need not enumerate them by name; and it 
may suffice to say that the author treats in a copious manner of 
their distribution, habits, and relation to man. In the conclu- 
ding chapters the arctic fauna is compared with alpine faunas, 
and an attempt is made to distinguish subdivisions in the direc- 
tion from east to west. 
Milne-Edward.s, II. et A. Recherches pour servir k Thistoire 
paturelle des Mammiferes. Paris, 1868-69. 4to. 
