20 GENERAL REMARKS ON THE EGGS OF MARINE FISHES. 



greatly reduced, and eggs can be transmitted, for instance, from 

 Shetland to St Andrews with comparatively slight loss. Even 

 though kept for ten days without renewal of the sea water, and 

 the eggs hatch on the way, the lively little cod, with their 

 characteristic black pigment-bars, swim actively near the surface 

 of the water, darting hither and thither when interfered with, 

 while a stratum of the dead lies on the bottom. The water 

 may even be somewhat milky and the odour perceptible, and 

 yet the larviB survive — until, as Sars also found, the yolk-sac, 

 which supplies them with nourishment, is absorbed. 



Throughout the spring and summer countless hosts of these 

 little eggs belonging to many species, varying slightly in size and 

 structure, float about near the surface and in mid-water, tossed 

 here and there by the waves and at the mercy of every tide or 

 current. At certain spots off the coasts, at the meeting place 

 of currents, these eggs accumulate in millions and may then be 

 taken in any numbers by dragging fine tow-nets through the 

 water. During the wanderings of these eggs the development 

 of the embryo inside progresses slowly but surely, until through 

 the transparent tissues the principal organs and shape of the 

 future little fish can be clearly discerned, and soon after the 

 lively movements of the same cause a rupture of the egg- 

 membrane, which, no longer required, sinks to the bottom of the 

 sea, leaving the helpless larval fish to toss about in the surface- 

 water until it gradually gains size and strength to regulate its 

 own movements and to hunt for the minute crustacean organisms 

 upon which it feeds. 



Number of floating eggs diagnostic of number of breeding 

 fishes. The condition of the fish-fauna of the various grounds 

 may to some extent be estimated by the number of the eggs 

 floating near the surface. It has been seen that Sars found 

 the water crowded with a multitude of eggs off the Loffoden 

 Islands, where enormous numbers of cod are captured. In our 

 seas no fishing bank is so prolific, the greatest number of eggs 

 occurring on Smith Bank, off Caithness, and the next on the 

 rich grounds off the Island of May — both of which present a 

 great contrast with the meagre supply of eggs of round fishes 

 floating in St Andrews Bay. The proportional numbers in each 



