BONY FISHES 277 



either deficient or excessive pressure is as dangerous to fish as it is to 

 man. (What happens when surface fish sink to too great a depth or 

 deep-water fish rise too near the surface ? See air-bladder.) 



8. Reproduction. All fish, with the exception of a few species, 

 which, like the blue shark, bring forth living young, are oviparous. The 

 number of eggs deposited by the female is immense ; nor is the 

 reason of this difficult to understand when we consider that the parents 

 take no further interest in the fate of their eggs after they have 

 deposited the spawn, that thousands of eggs and young fish are 

 destroyed by fish of the same or other species, or other predaceous 

 animals ; whilst, lastly, an incessant internecine war of extermination is 

 constantly being waged amongst the fishes themselves, in spite of their 

 peaceful appearance and demeanour. In some fish, e.g., the cod, the 

 eggs deposited by one female amount to several millions. Man also 

 takes no small share in the destruction of fishes. Many millions of 

 people live year in, year out, from the capture of fish and the various 

 industries connected with this calling. Several species nurture their 

 young (give examples). The young, after they leave the egg, in many 

 cases (e.g., eel and lamprey) pass through a series of developmental 

 changes (metamorphosis), such as we saw among the amphibia. 



ORDER I. : BONY FISHES (TELEOSTEI). 



SKELETON bony, the vertebrae separate. Skin, as a rule, furnished 

 with true scales. A gill-cover (operculum) always developed. 



Sub-Order I : Air-bladder provided with an Air-duct (Physostomi). 



The Carp (Cyprimis carpio). 

 (Length generally 12 to 17 inches. See illustration, p. 274.) 



A. Habitat and Range. 



The native home of the carp is probably in the temperate parts of 

 Asia. On account of its well-flavoured flesh, however, man has extended 

 the range of this fish over a great portion of the earth, and in many 

 places (Germany and America) it forms the principal object of fish 

 culture. Its wide distribution under the most varying conditions of life, 

 and the fact that it can be bred like a domestic animal (see dog), have 

 led to the development of numerous breeds or varieties. Of the latter 

 we need only mention the Smooth or Specular Carp, with a few large 

 scales, and the Leather Carp, which is perfectly devoid of scales (explain 

 the names). 



