160 EGGS AND FRY OF THE HEERING 



Dr. Lebour, who found that 725 of them contained no 

 perceptible food at all. The yolk-sac, which is absorbed, it is 

 believed, in throe or four days, was present in the case of many 

 specimens up to 0-35 inch long, but Dr. Lebour has long since 

 discovered that the larvae start feeding— as do young turhot — 

 ivhile the yolk-sac is still present and tvhen they are no larger 

 than 0-27 inch. Their diet seems to be varied. In the very 

 early stages, herrings feed largely on greenish matter, diatoms, 

 and single-celled animals like peridinians,i flagellates, and in- 

 fusoria. At a later stage they contain the free-swimming larvae 

 of snails (gastropods), bivalves, copepods, and barnacles ; also 

 young adult copepods and other small animals. 



Reference has already been made more than once to Einar 

 Lea's discovery that whole broods of Norse herrings have 

 perished in certain years — and this point will be again referred 

 to. It is fairly clear to the writer's mind that the eggs of 

 herrings are not in much danger except from predaceous fish 

 and animals. Does famine wipe out whole broods of baby 

 herrings during the critical days when they are living on the 

 yolk-sac and gradually acquiring the habit of digesting other 

 food ? If so — inasmuch as baby herrings live at the bottom till 

 the sac is absorbed, and at mid-water for some months after- 

 wards, what causes this famine ? Why — if ever — are the 

 minute plants and animals, on which baby herrings feed, absent 

 from the bottom or the middle waters during the few weeks in 

 which the fish must find them or die ? Answers to these ques- 

 tions might help herring-curers and exporters to forecast their 

 harvests years ahead. And yet — ^just because ^Science never 

 explains — curers and exporters are apt to speak with very scant 

 respect of investigations so ' unpractical ' as the study of 

 ' plankton '. 



Dr. Fulton maintains that adult herrings get most of their 

 food in the water which they ' exhale ' in the process of breath- 

 ing. Just as the Greenland whale and the blue whale, with 

 their huge tongues, press the water out of their mouths through 

 a whalebone fringe which entangles the tiny animals on which 

 they live, so does the herring strain the water through the fine 

 grating formed by its gill-rakers, for the food which is floating 

 in it. It follows, therefore, that though a herring can, and does, 

 pick out any particular object wdiich takes his fancy — including 

 (sometimes) a trout-fly — he does not as a rule discriminate much 

 in his diet. If the animal is caught in the gill-rakers it is 



^ Peridinians are claimed as plants by botanists, and as animals by some 

 zoologists ! Flagellates have no skeletons, but are apparently distinctly 

 ' animal '. 



