J. PISCICULTURE AND THE FISHERIES. 453 



German pisciculturists have lately been endeavoring to ascer- 

 tain the causes of this very inconvenient occurrence, with a 

 view of applying a practical remedy. According to some, it 

 is produced by the freezing over of the pond, and the accu- 

 mulation of snow on the resulting ice, exercising a pressure 

 upon the Avater which materially affects the respiratory func- 

 tions of the fish. This can hardly be a sufficient reason, how- 

 ever, since the resulting pressure is very slight compared to 

 that which the same fish may experience at difierent depths 

 in large bodies of water. Another alleged cause is the un- 

 timely disturbance of the fish, in various ways, before they 

 have had their full measure of winter's rest, this being the re- 

 sult of a premature awakening of the fish, or of the intrusion 

 of pickerel, or other predaceous species. Dr. Fraucnfeld, 

 however, is inclined to believe that this may be partly the re- 

 sult of the development of microscopic fungi in the water, es- 

 pecially as a common premonition consists of a change in the 

 color of the water, which becomes turbid and altered in ap- 

 pearance, in consequence of the development of the fungi in 

 large numbers. The effect of this is to use up the oxygen, 

 and introduce into the water an excess of carbonic acid gas, 

 thus rendering the water insufficient for proper respiration 

 on the part of the fishes. With this suggestion, reference is 

 made to the fact that certain fungi occasionally develop very 

 rapidly on the surface of the snow, and that it is possible that 

 the snow fungus, or some other, may develop equally in wa- 

 ter of a certain minimum temperature, when the spores hap- 

 pen to fall into it. He advises, as the best method of reme- 

 dying the difficulty, and one in accordance with practical ex- 

 perience, to plant the edges of the pond with water-cresses. 

 This plant, as is well known, has a tendency to purify the 

 water by the decomposition of the carbonic acid produced by 

 the respiration of fish, thus restoring the eliminated oxygen 

 to the water. Verh. K, K. Zool Bot. Ges.^ Wie7i, 1872. 



MARITIME FISHERIES OF FRANCE FOR 1871. 



The Hevue 3Iaritime et Coloniale for December, 1872, con- 

 tains a summary of the maritime fisheries of France for the 

 year 1871, and indicates a gratifying improvement in this in- 

 terest as compared with the results for 1870. In that year 

 the country was just recovering from the effects of the war 



