LIFE-HISTORY AND DEVELOPMENT OF A FISH. 29 



on the 5th\ After standing an hour the majority were floating 

 on the surface, one or two lay on the bottom, while others rested 

 in mid-water. Placed in a vessel of water at 98° F. the eggs 

 exhibited lively movements for several minutes, being carried 

 up and down by the currents, but never remaining at the 

 bottom. The test-tube felt quite warm, yet the eggs floated, 

 and remained floating, as buoyantly in the warm water as in 

 the cold, so that their floating in the sea is not a question of 

 temperature. An interesting sequel, moreover, remains to be 

 told in connection with this experiment. The test-tube had 

 been placed aside and forgotten, but on May 10th while we were 

 explaining the matter to Prof Ewart of Edinburgh motion was 

 noticed in the dusty test-tube, and it was found that the eggs 

 which had been raised to a temperature of about 98° F. had 

 given birth to little fishes, which thus survived the exigencies 

 of their surroundings — both as regards temperature and water. 

 On the other hand severe frosts are fatal to eggs crowded in 

 shallow vessels, in many cases actual rupture taking place, and 

 the same occurs with large eggs, such as those of the wolf-fish, 

 deposited on the bottom of the vessel. Thus to take the 

 example of the eggs of the haddock during a severe frost in 

 February. The earlier stages had been successfully passed, 

 when the water at the surface of the vessels was frozen into 

 soft flakes of ice — on which many of the eggs were elevated. 

 No sooner was this ice broken than all the eggs were observed 

 to present a whitish opacity and to sink to the bottom. Some 

 of those which had floated in mid-water, or under the trickle 

 from the supply-pipe, escaped destruction, but in a few days 

 they also succumbed during a night of unusual severity, and 

 after the embryos had been outlined. These circumstances, 

 however, are for the most part artificial, for in the sea the 

 danger from such extreme cold would be minimised, since the 

 eggs in winter and spring are generally some distance from the 

 surface ^ 



Out of the little glassy sphere, after a longer or shorter 

 interval (varying from a few days to a few weeks, according 



1 Nature, vol. 31, p. 555. 



2 Ibid., vol. 34, p. 148. 1886. 



