THE INTERNATIONAL FISHERIES EXHIBITION. 235 



are subjected, fish are provided with a large amount of ova, which 

 is mostly sufficient to counterbalance natural waste. Thus eleven 

 millions of eggs have been taken from a 21 lb. Codfish ; 550,000 

 from a Mackerel ; 239,775 from a 4 lb. Brill ; while a Salmon 

 deposits about 800 for every pound's weight of the parent fish. 

 Although most forms are polygamous, some are monogamous. 

 The period of the year at which spawning occurs, the size of the 

 eggs, the depth of water in which they are deposited, the time 

 they take incubating, and the places selected for the ova, are 

 exceedingly varied. 



The eggs of Cod float in the sea until the } r oung emerge, 

 those of the Herring sink to the bottom, where, by means of a 

 glutinous substance, the}' are attached to sea-weeds, rocks, and 

 other objects ; those of some species of flat fishes float so long as 

 the water is agitated, subsiding when it is smooth. One form of 

 Sea-sucker (Lepidogaster) affixes its eggs to the inside of a dead 

 sbell as a butterfly does to a leaf. The Garfish (Belone) has fila- 

 ments springing from the outer covering of its ova, which enables 

 them to adhere together in a mass, or attach themselves to con- 

 tiguous substances. Anadromous forms deposit their eggs in 

 running waters, but in different ways ; thus the Smelt affixes its 

 ova to planks, stones, &c, near high-water mark ; the Salmon and 

 Trout cover theirs with gravel ; while the Grayling deposits it on 

 the bed of the river. Perch and most Carps attach their eggs to 

 water-weeds, Sticklebacks construct a nest, while in the tufted 

 gilled fisbes, represented by the Pipe- and Horse-fishes, the male 

 undertakes the functions of a nurse, the eggs for this purpose, up 

 to the period of the evolution of the young, being retained 

 between the ventral fins, as in certain Pipe-fishes (Solenostomus) , 

 in tail-pouches, as in Horse-fishes {Hippocampus), or in receptacles 

 on the breast or abdomen, as in the Pipe-fish [Doryrhampkus), or 

 merely in two rows in the same position, as in Nerophis. The 

 males of some tropical Sheat fishes or Siluroids also perform 

 maternal duties by carrying" the eggs about in their mouths until 

 the young are hatched. In some forms, as Lampreys, the expul- 

 sion of the roe is mechanically assisted by the two parents fixing 

 their sucker-like mouths to a convenient rock and entwining them- 

 selves round one another. Also in Carps, as in the common 

 Goldfish, the male has been observed to roll the female over and 

 over at the bottom of an aquarium until her eggs have become 

 expelled. 



