A? FISHES CHAP, 
large oil globule on the surface of the yolk, and not infrequently 
the yolk becomes partially or completely broken up into small 
masses. Pelagic eggs are always non-adhesive and free, and they 
invariably belong to marine Fishes. Amongst the British food 
Fishes which produce pelagic ova may be mentioned the Gadidae 
(e.g. Cod, Whiting, Hake, Ling), the Pleuronectidae (e.g. Turbot, 
Brill, Sole, Plaice), Scombridae (e.g. Mackerel), Triglidae (e.g. the 
Gurnards), Percidae (e.g. the Bass), and Clupeidae like the Pil- 
chard and Sprat, but not the Herring, whose adhesive demersal 
eggs are deposited in clumps on shingly banks in the sea at 
varying distances from the shore. 
The eggs of Elasmobranchs are deposited singly or in pairs at 
0G 
Fic. 235.—Diagrams of the pelagic ova of a Cod or a Plaice (A) and of a Ling (Molva). 
G, Germinal disc ; 1, micropyle; 0.G, oil globule; Y, yolk. (From Cunningham.) 
considerable intervals, and the period of egg-laying is prolonged 
over a considerable part of the year. In most other Fishes, as in 
Teleosts, the period of spawning is limited to a few months, 
usually in the spring and summer in temperate latitudes; and in 
the case of a single Fish it may last only a few days or weeks, 
but the number of eggs produced is often enormous. Thus, in a 
Ling 61 inches long and weighing 54 pounds the ovaries con- 
tained 28,361,000 eggs. A Turbot, 17 pounds in weight, had 
9,161,000 eges; and a Cod of 214 pounds 6,652,000. The 
least prolific of the British food Fishes is the Herring, in which 
the number of ovarian eggs varied from 21,000 to 47,000 in four 
specimens examined,’ The extraordinary fecundity of many Fishes 
seems to bear no relation to the relative abundance of the Fishes 
themselves, but rather it is to be associated with certain disad- 
1 Cunningham, op. cit. p. 69. 
