26 



FISHES. 



(I'lSCI'S.) 



This <'l;iss ciiibraces ;ill tlmse iiiliabitants of the water who cannot live any time mit of it ; 

 they swim by means of tins, breathe b}' gills, wiiere the blooii, which is eolil, comes in contact 

 with the oxygen in tlie water for the aeration of their system. Tiieir gills breatlie water as the 

 Inngs of other animals lireatlie air. Tlie reason a tish dies wlien it is taken ont of the water is 

 l)ecanse the di-lirate gill membranes become dry and collapse against each other, so that the 



circulation of the blood is stopped, and the oxygen of the 

 atmosphere can no longer act upon it. The blood is cir- 

 culated by a, heart witli two chambers, an auricle and a 

 veutriele, which lies just behind the gills. In nearly 

 every instance tish })ropagate their sjiecies by means of 

 eggs, and are, therei'ore, called oviparous. The j>ro])elling 

 power of the tish is almost entirely supplied by the tail, 

 the tins being almost exclusively used for balancing. The 

 tins are termed "dorsal,"' ''pectoral,'' "anal,"' "abdominal."" 

 and •• caudal " or tail. The dorsal tins are situated on the 

 back, tlie pectoral on what might be called the shoulders, 

 the anal near the vent, the abilominal or ventral may be 

 said to correspond with the hinder liml)s of quadrupeds, 

 whilst the caudal is commonly known as the tail. The 

 scales are beautifully constructed, overlapping each other 

 closely, and forming a natural sheathing, to allow of swift 

 progression through the water. The skin of the fish is 

 supplied with jiores, which ]iermit of the exudation of a 

 secretion of a mucous substance which nature supjilies 

 as a lubricator. On most fishes will be observed a lateral 

 streak or line extending from the head to the tail, whence 

 this lubrication jirincipally exudes; the scales on this 

 line are perforated. The lateral line is supplied with 

 nerves, and is termed tlie muciferous system. The optic 

 nerve of hshes varies in diti'erent species; in some cases the 

 nerve leads straight to the brain, in others the nerves 

 cross so that the right eye is connected with the left side 

 of the brain, and vice versa; whereas in the case of rays, 

 sharks, &c., the optic; nerves join, and lead in a united 

 band to the liraiu. The arrangement of the bones is so 

 complicated and peculiar that reference to the illustration 

 below will give a better idea of the subject than pages of 

 descrijition. 



Fish are of distinct sexes, and are almost entirely 

 ovi]iarons, the eggs being deposited by the females, 

 fertilization by the male taking jdace immediately after- 

 wards. 



As can be well iindei'stood, the majority of fish in 

 this Acjuarium are those which are termed littoral oi- 

 shore-fisri ; pelagic or deeji-sea fish lieing ditfi(Uilt to 

 obtain, and also more difficult to maintain alive under 

 artificial conditions, as they are not so acc^ustomed to (dianges of teiii|ieratiire and density of water 

 as the fish which fre(|Ueiit the shores of our coasts. 



By the naturalist fish are classed under a number of orders, such as — Acanthopterygii or 

 spine-finned, which is the most eoinprehensive ; Acauthini, with vertical and ventral fins, without 



ll:KI' \i:kii 



SPK<'1MKN SHdWINC 

 IIROANIS.M OF KISII. 



INTEKXAI. 



