94 INTEODUCTION AND BEEEDES^G OF FISH. 



rabbit — wbich, even when reared in warrens, is still a half-wild 

 animal— at 30,000,000. 



Of course natural reproduction can not keep pace with this 

 enormous destruction, and many animals of much interest to 

 natural science are in imminent danger of final extirpation.* 



Large Marine Anvmals relatively vnimjoortami in Geogra^phy. 



Yast 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 locahty might very probably lead, in time, 

 to the formation of a bank, which, in connection with other 

 deposits, might perceptibly affect the hue 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 o/nd Breedi/ng of Fish. 



The introduction and successful breeding of fish of foreign 

 species appears to have been long practised in China, and was not 

 unknown to the Greeks and Romans.f This art has been revived 



* 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 animals, 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. 



f The observations of CoLUsrELLA, de Re Rustica, lib. viii., sixteenth and 

 following chapters, on fish-breeding, are interesting. The Romans not only 

 stocked natural but constructed artificial ponds, of both fresh and salt water 



