xviii 



Second Annual Report of the 



Scientific # By studying the effects of temperature during development, it 

 nves^iga^ions. wag f oun( j t j iat w ^ a temperature of 53° Fahr. and upwards, the 



Effects of eggs hatched in about eight days, while with a temperature of 38° 



curate^?™ Fahr. the hatching was delayed until about the fortieth day. 



development. When the temperature was from 50° to 51 0, 8 Fahr., the hatching 

 occurred on the eleventh day, but when the eggs were placed 

 during the first three days of development in water with a 

 temperature of 33°-8 to 35°'6 Fahr. (1° to 2° C), and then removed 

 to water with a temperature varying from 50° to 53°*6 Fahr. 

 (10° to 12° C), the hatching was delayed from four to five days. 



On the other hand, it was found that cold had a greater retarding 

 influence immediately before the time of hatching than it had 

 during the early stages of development, for eggs which had been 

 developing in water at 51 0, 8 to 53°*6 (10° to 12° C), and which would 

 have hatched in two days when introduced into water with a 

 temperature of 35°*6 Fahr. (2° C), did not hatch for twelve days, 

 the time being thus increased from ten to twenty days by the 

 change of temperature. It was also found that in the brackish 

 water of the Baltic, while the eggs developed satisfactorily at a 

 temperature of 33 0, 8 Fahr. (+ 1° C), the development did not 

 proceed in a normal way when the temperature was reduced to 

 30 o, 56 Fahr. ( — 0°*8 C). These experiments indicate that any of 

 the spawning grounds of the winter herring might be rendered 

 unsuitable by the approach of cold polar currents ; in other words, 

 that the disappearance of herring from their usual spawning banks 

 has perhaps sometimes resulted from a lowering of the bottom 

 temperature. 



Size of fry Other experiments showed — (1) That the length of the fry when 

 when hatched, hatched varied with the time required for development, the fry 

 measuring about £ of an inch (5*4 mm.) when the development 

 was rapid, but measuring about J of an inch, and having a some- 

 what smaller yolk bag, when the development was prolonged. 

 Food of fry. (2) That the fry of spring herring, which were hatched in fourteen 

 days, and kept in the open water of Kiel Bay, with a temperature 

 varying from 51°'8 to 68° Fahr. (11° to 20° C.) lost their yolk bag in 

 three days, and in five days began to feed on embryos of molluscs 

 (such as Mya, Cardium, Tellina, Rissoa, Lacuna, and Ulvse), and 

 later on copepods. 



(3) That the fry grew according to the following table : — 



Rate of growth Fry 1 month after fertilisation of eggs were 10-11 mm. in length, 

 of young „ 2 months „ 17-19 



„ 3 „ 30—35 „ 



„ 4 „ „ 48-58 



„ 5 „ „ 65-70 



Herring. 



Compared with what was believed to be the natural rate of growth 

 in Kiel Bay, the fry under observation grew during the earlier 

 months very slowly ; but on taking steps to provide them with an 

 abundant supply of their natural food, they rapidly made up for the 

 slowness of growth, and at the end of the fifth month they were as large 

 as the fry of a similar age that had developed naturally in the Bay. 

 whitehait (4) That about the end of the third month the scales begin to 

 stage at 3rd appear, and the fry reach the ' whitebait ' stage. At what rate they 



