But so far as numbers are concerned, the statistics of the furtrade furnish the most surprising results. Russia sends annually to foreign markets not less than 20,000,000 squirrel skins, Great Britain has sometimes imported from South America 600,000 nutria skins in a year. The Leipzig market receives annually nearly 200,000 ermine, and the Hudson Bay Company is said to have occasionally burnt 20,000 ermine skins in order that the market might not be overstocked. Of course natural reproduction cannot keep pace with this enormous destruction, and many animals of much interest to natural science are in imminent danger of final extirpation. [Footnote: Objectionable as game laws are, they have done something to prevent the extinction of many quadrupeds, which naturalists would be loth to lose, and, as in the case of the British ox, private parks and preserves have saved other species from destruction. Some few wild aminals, such as the American mink, for example, have been protected and bred with profit, and in Pennsylvania an association of gentlemen has set apart, and is about enclosing, a park of 16,000 acres for the breeding of indigenous quadrupeds and fowls.] LARGE MARINE ANIMALS RELATIVELY UNIMPORTANT IN GEOGRAPHY. Vast as is the bulk of some of the higher orders of aquatic animals, their remains are generally so perishable that, even where most abundant, they do not appear to be now forming permanent deposits of any considerable magnitude; but it is quite otherwise with shell-fish, and, as we shall see hereafter, with many of the minute limeworkers of the sea. There are, on the southern coast of the United States, beds of shells so extensive that they were formerly supposed to have been naturally accumulated, and were appealed to as proofs of an elevation of the coast by geological causes; but they are now ascertained to have been derived chiefly from oysters and other shell-fish, consumed in the course of long ages by the inhabitants of Indian towns. The planting of a bed of oysters in a new locality might very probably lead, in time, to the formation of a bank, which, in connection with other deposits, might perceptibly affect the line of a coast, or, by changing the course of marine currents, or the outlet of a river, produce geographical changes of no small importance. INTRODUCTION AND BREEDING OF FISH.