of the Fishery Board for Scotland. 



115 



Temperature of the Water in which the Uncooled Eggs of the fifth lot of 

 Spawn were kept. Degrees centigrade. The temperature was not 

 taken oftener than once a day. 



Gooled Spaion : Vc. — March 6. — Part of the spawn of the Fifth lot was 

 put into hatching boxes in cooled water. In order to assist the aeration the 

 boxes were lifted, almost every day, for a little distance, and then pressed 

 down into the water. The water rushed in through the sieve-bottom among 

 the gravel and sent the loose spawn flying about. 



March 9. — The eggs were examined. They were in the stage shown in 

 fig. 2. A good number of the single eggs were dead. 



March 14. — Some pieces of spawn were taken from one of the hatchery 

 boxes and put into a metal egg-box which had been half filled with large 

 pebbles. The lumps of spawn Avere attached to gravel ; they were large, 

 flattened in shape. All appeared to be alive. The box was surrounded by 

 ice, and will be referred to as Yc ^ . 



March 15. — Yc. — By means of a sieve the majority of the dead single 

 eggs were removed. The dead eggs showed a perivitelline space, but it is 

 doubtful if they had all been fertilized. A portion of an ovary was found in 

 one of the boxes. The eggs on the end of the piece where they were 

 uncovered were all fertilized. The little groups of eggs were mainly alive, 

 although dead eggs were noticed among them. The living eggs were at the 

 stage of the closure of the blastopore. {Of. figs. 51, 5, 6, 27). 



March 29. — Yc— The tip of the tail of the embryo reached round to the 

 nape of the neck (c/. fig. 11). The eyes Avere beginning to show a general 

 shading as if towards pigmentation. The heart was beating. Some of the 

 spawn was shifted on this date from cooled water of 3° into the ordinary 

 hatchery water at 6-5° C. It was thereafter kept at the ordinary tem- 

 perature. It was labelled Vc^. 



March 30, April 2, 5, 6. — Yc^. — No fry was found in the box. 



April 10. — Yc^. — Some fry was obtained on this date. The water flows 

 into the box at the top and escapes by the sieve-bottom. Owing to the 

 presence of the gravel and spawn on the bottom it is not possible to remove 

 all the larvae that are free on any date unless the spawn is taken out of the 

 box also. All the fry that was accessible (visible) was removed on the 

 dates specified, so that the appearance of fry in the box on the following day 

 meant that a certain number had hatched out during the night. In other 

 cases the water, flowing out of the box in which the spawn was, escaped from 

 the top of the box and carried away the fry as they were hatched. These 

 were captured in hatching-boxes, which could be emptied each day. It was 

 thus possible to make sure of the exact date of hatching. This arrangement 



