152 NATURAL SCIENCE. march, 



f inch in length." This inquiry is, of course, not without its practical 

 bearings, and is sure, ultimately, to prove of value to those who 

 desire a more scientific cultivation of the harvest of the sea. 



Fish-Culture. 



The importance of that scientific intervention with nature in 

 connection with the increase of our marine food-supply, to which we 

 have just alluded, was well brought out by Mr. J. J. Armistead in his 

 recent discourse at the Royal Institution. It was the opinion of 

 Frank Buckland that, in nature, not one egg per thousand produced 

 a mature fish. By fish-culture, on the contrary, 95 per cent, of the 

 eggs laid down are hatched, while of these one-half can, under favour- 

 able conditions, be brought to maturity. Roughly speaking, the yield 

 is increased five-hundred-fold. The methods employed must in the 

 first place simulate nature, as, for instance, when the boxes contain- 

 ing pelagic ova are moved up and down so as to produce the effect 

 of wave-motion. Secondly, they must enhance all the favourable 

 conditions, such as the supply of oxygen, the absence of light, the 

 furnishing of sufficiently small and nourishing food ; fish get indiges- 

 tion from artificial foods, and it is to be noted that they travel better 

 on an empty stomach. Thirdly, it is necessary to counteract the 

 numerous adverse influences that are so common in a state of nature, 

 and this applies, not merely to the artificial rearing of fish, but to their 

 preservation generally. No less than thirty diseases are known and 

 diagnosed, and for many of them cures have been found. Accidents 

 of deficiency of water or food in running streams should be guarded 

 against with the help of dams and reservoirs. At the present time 

 our salmon are much neglected in this respect. Whether from lack of 

 food, irregularity of water-supply, differences of specific gravity or 

 temperature, the herring deserted the Firth of Forth some forty years 

 ago and have not yet come back. 



The great advance made in this subject during the last thirty 

 years, and the success that meets the attention paid to it by the 

 Governments of Germany and the United States, suggest that we have 

 here a source of national wealth that might well receive more direct 

 care from our own Government. 



Preservation of Marine Mollusca. 



Those who were interested in Mr. Hornell's paper on Formalin 

 (Nat. Sci., vol. vii., p. 416), may like to learn that this fluid has been 

 tried for the preservation of Aplysia and Pleuvobvanchus. In both 

 cases, however, a considerable amount of colouring matter was 

 dissolved out of the integument. Dr. J. D. F. Gilchrist, who con- 

 tributes this observation to Professor Herdman's Report, also records 

 a method of killing Aplysia in an expanded condition, which he says 



