WHY SPAWNING -BEDS ARE MADE BIT BY BIT. 181 



We have seen that the bed, or trench, in which 

 salmon deposit their spawn, is made bit by bit, 

 and no doubt the inquiring reader will ask why ? 

 I have, I hope, a ready and satisfactory answer. 

 The ova of the female salmon are not mature all at 

 the same time. That portion of them next the 

 vent becomes first ripe for deposition, whilst the 

 part in the pectoral regions is immature. In con- 

 sequence, the ova can be deposited by piecemeal 

 only, and that is one of the chief reasons why the 

 salmon-bed consists of a succession of excavations, 

 the first for the reception of the ova next the vent 

 which are already mature ; the second for the ova 

 that will 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 in- 

 tervals, as their outward covering or shells harden, 

 that is as they become mature. The analogy ex- 

 tends 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. 



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