64 PHYSOSTOMI. 



" brackish water " only for about two hours at each high tide, but not at all during 

 the neaps, while this brackish water is so diluted as to differ but little from fresh 

 water in specific gravity, the tide serving as a dam to the river water, and by 

 obstructing its free outflow, causing its accumulation and overflow. The foregoing 

 instances occurred near the mouths of small rivers, and should their state be such 

 — due to pollutions or insufficiency of water — that Salmonidce are unable to ascend, 

 they may drop or deposit their ova in the sea or at the mouths of rivers ; but 

 suppose it is thus deposited, experiments have proved that the presence of salt 

 water is fatal to the fertilizing property of the milt, as also to the life of the 

 impregnated egg, should it come in contact with it. 



Sir J. Matheson, during the winter of 1860-61, had the following experiment 

 made upon two batches of fertile salmon ova. One lot was placed on a wire cloth in 

 a glass vase, wherein was brackish water which was daily changed, but they all 

 died at the end of the tenth day. The remainder were similarly treated, but with 

 fresh water, and in due time they all arrived at maturity. Mr. Sinclair (Field, 

 February 4th, 1882) remarks upon having taken about one hundred eyed ova, of 

 which two portions were enclosed in wicker baskets and buried in separate streams, 

 one of which was reached every tide by salt water, whereas the other was entirely 

 fresh. They were examined in about three weeks after one set of spring tides, when all 

 which had been reached by the salt water were found to be dead : not so those in 

 which the stream was entirely fresh water. The remaining third were hatched in 

 a wash-hand basin, in which was fresh water changed once a day. Dr. Davy also 

 instituted somewhat similar experiments with artificial saline water, from which it 

 appeared that a degree of saltness, almost or quite equal to that of sea water, is 

 pretty speedily fatal both to the ovum of the salmon and to the young fish : that 

 the same effect is produced on the young fish by brackish water of specific gravity 

 1016, but in a longer time, and that, when the solution is so diluted as to be 

 reduced to the specific gravity 1007, the advanced ovum may be hatched in it, and 

 the life of the young fish may be sustained in it for a few days, but with diminished 

 powers. 



The eggs of the salmon are small, round, elastic bodies, of a clear white, pink, 

 or even coral colour. Due to their tough outer coat they are very elastic, as may 

 be seen by throwing one on the ground, from whence it will rebound like an india- 

 rubber ball. This strength and elasticity we know must be an exceedingly 

 important property if we remember where these eggs are deposited and what an 

 amount of pressure they may have to undergo. Toung salmon are hatched from 

 eggs deposited in rivers, not near to its mouth, where the tide or the current 

 would be too strong for the young fish to live in, but in small and often 

 mountainous streams, where the water is pure and shallow, having a gravelly 

 bed which permits the redd or nest to be constructed, while deep pools in the 

 vicinity allow the breeding fishes to retire into them for rest. The salmon 

 ascends our rivers to a suitable spot, and in the gravel at the bottom of the 

 stream constructs its redd, which work would seem to be the occupation of 

 the female. She lies on one side, and, by moving her tail rapidly from one side 

 to the over, fans up the gravel until she gradually sinks into a kind of trough, the 

 male remaining near, ready to give battle to any intruder. For this purpose his 

 lower jaw is furnished at this period with an offensive weapon in the shape of a 

 cartilaginous, hook-like process. The female (waited upon by the male) now 

 deposits her eggs in the trough she had made, and these are fertilized by the 

 male, and subsequently covered with gravel to some feet in depth, the whole forming 

 a redd. 



She now falls back into one of the deep pools, until she has acquired sufficient 

 strength to again shed more eggs. During this period the salmon (similar to the 

 shad and many other fishes) is indisposed to feed, and lives on the stock of fat it 

 has laid up while resident in the sea. It has been computed that every female 

 salmon deposits about nine hundred eggs to each pound of its weight, and that 

 only nine hundred of these in every 17,000 shed in British rivers ever attain the 

 parr stage. As might be anticipated, eggs deposited in a running stream are very 

 liable to be carried away by the current, and the places selected by salmon for 



