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Part III. — Twenty-seventh Annual Report 



IV.— EXPERIMENTS TO SHOW THE INFLUENCE OF COLD IN 

 RETARDING THE DEVELOPMENT OF THE EGGS OF 

 THE HERRING {GLUPEA HARENGUS, L.), PLAICE 

 {PLEVRONECTES PLATESSA, L.), AND HADDOCK {GADUS 

 jEGLEFINUS, L.). By H. Chas. Williamson, M.A., D.Sc, 

 F.R.S.E., Marine Laboratory, Aberdeen. 



(Plate I.) 



CONTENTS. 



Introduction, ..... 



The Different Lots of Spawn, 



Lots I., II., and III., .... 



The Cooling Arrangement, 



Table of Temperature of the uncooled water of Lots I., II., and III, 

 ,, ,, ,, ,, ,, cooled ,, ,, ,, ,, ,, ,, ,, 



Fourth Lot of Spawn, ...... 



Table of Temperature of the Fourth Lot of Spawn uncooled, 



,, ,, ,, ,, ,, ,, ,, ,, ,, cooled. 



Fifth Lot of Spawn, ...... 



Table of Temperature of the Fifth Lot of Spawn uncooled, 



)) )) „ ,, ,, ,, ,, ,, ,, cooled. 



Sixth Lot of Spawn, ...... 



Meyer's Experiments on the Incubation of the Eggs of the Herring at Kiel, 



Summary of Experiments in Laboratory, 



Crystals found inside the zona, . 



Fertilization of the Eggs of the Herring, 



The Herring Larva, .... 



The Transport of Living Adult Herrings, 



Experiments on the Pelagic Eggs of the Haddock and Plaice 



Experiments on Turbot, . . 



Explanation of Plate I., 



PAOtK. 



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The Government of New Zealand has requested the Fishery Board for 

 Scotland to carry out certain experiments bearing on the retardation of the 

 development of the ova of the herring. Information was desired as to 

 whether it was possible to prolong the period of incubation to 50 days, an 

 interval which would admit of the eggs being conveyed from this country to 

 Now Zealand before they hatched. 



Since the period of incubation depends, within limits, on the temperature 

 of the water, the retardation of development is a matter of maintaining the 

 eggs at a suflSciently low temperature. I was asked by Dr. Fulton to make 

 these experiments, and I have been able to show that the period of incuba- 

 tion may be extended to 50 days. Some embryos were in the egg for a 

 longer period. 



The eggs upon which the experiments were made were obtained at 

 Anstruther in February and March 1908, during the winter herring fishing 

 in the Firth of Forth. Since the ova of the herring are adhesive, it is con- 

 venient to have them spread on glass plates. This facilitates examination 

 from time to time, and simplifies the arrangements for transport. 



On February 17 very few herrings were being caught, and of these the 

 majority were not yet ripe. There was, however, a proportion of them in the 

 running condition. The herrings were being caught close inshore, where 



