EXPERIMENTAL WORK. 227 



rapidly to the twentieth ; then falls very rapidly, and 

 on the thirty-first day the loss in packing, if the handling 

 is skilful, is almost nil. 



The answer to Mr. Buckland's first query is therefore : 

 " Pack as soon as the eggs arrive, but so as to be able to pick out 

 the ova killed before the ship sails, without disturbing the rest." 

 B. Freezing eggs I have only tried with Loch Leven ova. 

 In all cases where the ovum has been frozen solid in 

 water, it has turned white on being thawn out. Where 

 the eggs have been only partially frozen, i.e. where a 

 film of ice has formed on the tray and partially involved 

 part (some) of the ova, the loss has been partial, the ova 

 involved showing white specks some large, and some very 

 small indeed. All those with large white spots died in 

 a few weeks ; in the case of some with small specks, the 

 specks enlarged, and they also died. In the case of about 

 half the eggs involved, the development stopped ; but 

 they did not turn white till due to hatch, while some few 

 eggs actually hatched into puny alevins. A number burst 

 when about due to hatch, or a little before. Eggs which 

 I froze dry in air, and afterwards thawed out in snow- 

 brae, hatched without any obvious injury. There is room 

 for many more experiments in freezing ova ; those con- 

 ducted were with eggs in which about 40 per cent, of the 

 period of incubation had been accomplished. Livingston 

 Stone mentions (Domesticated Trout, p. 146) that alevins 

 will stand cold wonderfully ; and that he had frozen them 

 (apparently in air) so that they were glued tight on to 

 the ice, and that he had kept these " frozen thaws " by 

 themselves ; and that they appeared to do as well as any 

 trout of their age, and showed no signs of being injured 

 by freezing. The result of my experiment points to the 

 embryo being capable of standing great cold 10 or 

 20 F. below freezing without injury. But if frozen in 

 water, the embryo is injured by the pressure of the 

 ice, and probably by the spiculas of ice in formation. 



