218 AMBKICACST ANGLER'S BOOK. 



become next the vent and matured in four-and-twenty* hours, 

 perhaps, and so on for several days until all the eggs forming 

 what is called the 'hard roe' are ripe and fit to be laid. On 

 this point the common hen, and other birds, afford an analogy. 

 They deposit their eggs at intervals, as their outward cover- 

 ing or shells harden, that is, as they become mature. The 

 analogy extends no further. Birds' eggs are impregnated 

 before they are deposited ; Salmons' eggs are not ; birds' eggs 

 naturally require animal heat to vivify them, Salmons' eggs 

 never do. The analogy, therefore, applies only to deposition 

 or laying at intervals. 



" Let any one examine the roe of a female Salmon about 

 spawning-time, and the peas, grains, or eggs of that part of it 

 nearest the vent will always be found of larger size, and 

 softer than those situated higher up in the stomach of the 

 fish. They are softer also, and their outward filaments are 

 thinner and more porous, and thus they are fitter for impreg- 

 aation — for absorbing the milt of the male as it is poured 

 over them. There is another reason why all the ova cannot 

 be deposited at once. It is forced from the fish, or rather the 

 fish forces it from itself by pressure — by forcing itself into 

 the gravel of the nest. No natural pressure would be suffi- 

 cient to expel the ova at once. "When artificial pressure is 

 employed — I mean manual pressure — the mature ova alone 

 come freely away through the vent ; the immature ova remain 

 firmly enclosed within their reticulated tissues or membranes, 

 within, as it were, their net-work fastenings. Although the 

 unripe ova should be expressed, they would be useless for 

 production, for their absorbing pores . are still closed against 

 the interpenetration of the milt, and consequently in this state 

 impregnation is impossible. The milt of the male, like the 

 ova of the female fish, becomes mature by degrees. When 

 mature they are very easily exuded, for even holding up the 



