THE INFANCY OF FISHES 213 



ordinary transparency. So great is this that if a few be 

 placed in a bottle of sea-water they are practically in- 

 visible ; thereby, no doubt, enormous numbers are saved 

 from the maws of predatory fishes. The cod, haddock, 

 whiting, bib, poor-cod, poUack, coal-fish, plaice, flounder, 

 dab, and lemon-sole, lay eggs of this kind. In the case 

 of other floating eggs each is provided with a small globule 

 of oil serving as a buoy — as ior example in the rockling, 

 hake, ling, turbot and brill : the mackerel, grey mullet, 

 gurnard and bass. Why in some this oil-globule should 

 occur and not in others is as yet unexplainable. 



It goes without saying that eggs which are turned 

 adrift to float at, or near, the surface of the sea, are 

 extremely small : and this means that they are but ill 

 provided with yolk. Further than this, they are ex- 

 cessively numerous : not so much because of the loss by 

 predatory animals which must be provided for, as because 

 they are fertilised after extrusion, and this means that a 

 considerable percentage do not get fertilised at all. 



A notion of the enormous numbers laid by fishes which 

 disperse their eggs after this fashion may be gathered 

 from the estimates which have been made in the case 

 of many of our food fishes : the number increasing, be it 

 noted, with the size and weight-^that is to say with the 

 age of the fish. Thus, in a ling of 54 lb. the ovaries 

 contained 28,361,000 eggs, a 21-lb. cod, 6,652,000, a 

 haddock of i| lb., 156,000, another of 4 lb., 806,000, 

 a whiting of 10^ oz., 109,000 ; a flounder of i lb. 9J 

 oz., 1,638,000 ; a sole i lb. 10 oz., 409,000 ; a turbot 

 17 lb. 5 oz., 9,161,000. The "vigour" of the fish is 

 evidently another factor, for in two mackerel of the 

 same length, and differing in weight only by a quarter of 

 an ounce— the heavier fish weighing i8| oz.— the lighter 



