I MODERN INVESTIGATIONS OF THE SUBJECT 7 



floating spawn. Sars took some ripe eggs from the fish and put 

 some milt into the water containing them, and found the}- were 

 impregnated. The outline of the embryo was seen in the eggs 

 eight da}-s after the fertilisation, and in eighteen days the tender 

 little fish were hatched. 



The Norwegian naturalist considered that in consequence of 

 the condition of this floating spawn enormous quantities of it 

 were destro^^ed by the waves, or washed ashore, or driven to 

 distant places b}- the currents and the wind. He suggests, there- 

 fore, that it might be worth while to direct large quantities of the 

 spawn to places where it would be safe from the wind and waves. 



When he first became acquainted with it, Sars, as we have 

 seen, thought that the spawn of the cod was exceptional and 

 unique in its buo\^ant character. He soon found, however, that 

 this was b}' no means the case. He first found that the spawn of 

 the haddock was quite similar to that of the cod, and he also saw 

 three other kinds of floating spawn among the material collected 

 by his surface-net. In the summer of 1865 he visited the centre 

 of the mackerel fishery on the south coast of Norway, and found 

 that the eggs of the mackerel were also lighter than sea-water, 

 and floated about in the sea during their development. In 

 subsequent years the attention of Sars was given to the later 

 periods of the history of certain fishes, and to the general zoolog)- 

 of the sea : he did not extend his investigations of the mode of 

 spawning much more widel}-. But the subject was taken up b}- 

 other observers. In 1868, Malm, a Swedish professor, of 

 Goteborg, obtained and artificially fertilised the eggs of the 

 common flounder. The object he had in view was rather to see 

 the earliest stages of development, than to make out the conditions 

 under which the spawn is naturally shed and developed. But in 

 his published account he stated that the eggs were small, 

 transparent, and globular, separate and free in the water. He 

 does not state that they floated, but remarks that when disturbed 

 they remained suspended in the water a long time. These 

 observations were made on the coast of one of the islands off 

 Goteborg, and, therefore, it will be noted the spawning flounders 

 were taken in the sea, not in an estuary or a river. 



For some }-ears after this no important additions were made 

 in Europe to the number of fishes known to produce buo}-ant 

 spawn, but in the United States of America Professor Alexander 



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