SUITABLE TEMPERATURE. 165 



British salmon into the salmonless rivers of Australia, 

 by transmitting them packed in ice. In March 1858, 

 we wrote : " In order to prevent unnecessary pains to 

 protect salmon ova from the effects of cold, it should be 

 known that, if gradually applied, it does not injure 

 them, and that they have been known to be frozen up 

 in a sheet of ice without losing their vitality. Keaumur 

 demonstrated that the eggs of many insects are equally 

 uninjured by excessive cold." If this had been consid- 

 ered by those interested in the experiment of transmit- 

 ting salmon ova to Australia, the trial of the effect of 

 freezing ova might have been made years ago. 



The temperature of fishes, as we stated in the same 

 article, on the authority of Ltebig,* is from 2.7 to 3.6 

 higher than that of the medium in which they live ; 

 and as a warning that their ova are far more apt to 

 suffer from excess of heat than from excess of cold, we 

 related the failure of the attempt, made at our sug- 

 gestion, to rear young salmon at the Crystal Palace, 

 Sydenham. Instead of being in a temperature of about 

 40 Fahr., the ova, sent from the Tay, were placed in 

 the tropical department, contrary to our wishes, and 

 could not endure a temperature of about 60. In like 

 manner Mr Buckland's young fish sickened at the same 

 degree of heat arising from the direct action of the sun, 

 and were only saved by the prompt application of ice. 

 And the London pisciculturists have now arrived at the 

 conclusion that the young fry soon begin to pine if the 

 thermometer marks many degrees over 55. 



We have alluded to the inexpensiveness of the first 

 step in the process of pisciculture namely, collecting 

 and depositing the eggs. The hatching apparatus, our 

 readers will rejoice to learn, is neither costly nor cum- 

 brous. That patented by Mr Boccius, and sold at the 

 ridiculous price of 10, 10s., though capable of contain- 

 ing 25,000 salmon ova, is only two feet long by one 

 broad, and requires not more than four inches depth of 

 * ' Letters on Chemistry, ' p. 67. 



