182 SALMON. 



be for a time to its nature, in no long time for the most part 

 it is again impelled to press its course up tlie stream in spite 

 of hindrances; and yet again a change takes place, and the 

 same individual is equally eager to retrace its course. That 

 there is a necessity for these alterations of action is seen by 

 appearances of the fish which are subject to them; but in their 

 nature they are too obscure to be comprehended by us; although 

 we become aware of the existence of causes which hasten or 

 delay them in the instance of individuals. 



It was an early opinion, which is also supported by the 

 authority of Rondeletius, that the spawn of the Salmon was 

 shed and hatched in the sea; but late experiment has proved 

 that the presence of salt-water is fatal to the development into 

 life of the fertilizing property of the milt, as also of the 

 impregnated egg if it come in contact with it. It is also shewn 

 in the "Intellectual Observer," (April, 1864,) by the Eev. M. 

 J. Berkeley, that in a sluggish flow of fresh water or in a tank 

 the grains of roe are exposed to the danger of becoming covered 

 with a parasitic growth of vegetable fibres of several species, 

 which deprive them of the power of further development; and 

 this important observation may assist us in accounting for some 

 of the mishaps which have attended the attempts that have been 

 made to bring to life and educate the young fish which have 

 been taken from their native beds, and placed in tanks or 

 artificial beds. The presence of slime or mud is hurtful to the 

 egg or newly-developed young; and it is the opinion of observers 

 that the grains are injured if they lie in the gravel so near 

 as to touch each other. 



But when escaped through these various dangers much 

 difference of opinion has been expressed in reference to the 

 length of time during which the grains may remain buried 

 in the gravel, and consequently how long it is before they 

 manifest the active powers of their existence. Nilsson says 

 that in Sweden this is an hundred and thirty days, and in 

 Scotland it has varied from an hundred to an hundred and 

 forty; but so considerable a, difference as this may fairly be 

 judged to be connected with the warmth or coldness of the 

 climate and season; and from this we are at liberty to conclude 

 further, what is also shewn by observation, that in still warmer 

 districts, especially from the south and farthest west of 



