1896] Summary. 21 



mortality, it is true, was at first ratber great; but one cbief cause 

 of this may have been tbat the roe of one of the trout employed 

 was not fully ripe. In all, 200 young fish made their appearance, 

 this being a sufficient proof that development can be accomplished 

 under the above-named circumstances. It is worthy of remark that 

 the dead spawn turned white as in fresh water. 



In order to investigate the influence of brackish water on sal- 

 mon spawn that had been fertilized in fresh water, 100 pieces were 

 placed in a specml tank on the 4th Nov. 1895. The spawn had 

 been fertilized on the 3 Ist Oet., and since that date had lain in 

 fresh water. The saltness was maintained at between 7 and 8 per 

 mille. During the period from the 4th Nov. 1895, to the 24th 

 Feb. 1896, only 8 pieces died. The first young fish emerged on 

 the 17th Feb., and in all, 53 young fish made their appearance. 



On the 21st Jan. 200 pieces of salmon spawn (fertilized on the 

 31st Oet. 1895, and kept in fresh water until the 2 Ist Jan. 1896), 

 were placed in water of the above degree of saltness. The move- 

 ments of the embryoes in these could be distinctly observed with the 

 naked eye. Thirty of the above number diecl between the 2 Ist 

 January and the 17th February; but between the latter date and 

 the 14th March, 69 fish were hatched. It may thus be 

 considered an ascertained fact that both sea-trout and salmon spawn 

 can develop in water of which the saltness is from to 8 or 9 

 per mille. 



How far this saltness can be exceeded to any appreciable 

 degree cannot at the present moment be decided. It is hoped that 

 continued investigations will contribute towards the solution of this 

 question. It must also be remembered that all the spawn which 

 has yielded a positive result was fertilized in fresh water, except the 

 sea-trout spawn which was fertilized in water of 4 %o saltness. 



Although I believe, from the present investigations, that the 

 process of fertilization can be carried on in w T ater of a saltness 

 below the hitherto discovered limit for possible development, the 

 task still remains to establish this as an unassailable fact. 



