NON-RETENTION OF OVA. 95 



water, thereby to conceal the eggs, in degree at least, from 

 their numerous enemies lying in wait helow. 



When spawning has once commenced, it seems that the 

 male can no longer retain his milt, nor the female her roe, 

 the emission continuing under all circumstances. This has 

 been often noticed, even long after death. 



The female salmon leaves the spawning-bed many times 

 during the day, and makes little excursions about the river, 

 generally into the dead water above. At times these trips 

 are somewhat extended say to a distance of some seventy 

 or eighty paces. " But," said Mr. Keiller, " as from my 

 elevated position I could watch all her movements, I feel 

 perfectly confident that, during her absence from the 

 spawning-bed, she never in any way comes in contact with 

 the male fish. I am at a loss to understand the cause of 

 these trips. At times, I have thought it is for the purpose 

 of resting herself after the fatigue or exhaustion of spawning ; 

 at others, I have imagined it to be a special provision of 

 nature ; for if her original position were a bad one, and she 

 were to remain stationary, all her roe would be destroyed ; 

 whereas, by occasionally moving, as she does, about the 

 stream, and dropping her eggs as she goes, some of them, at 

 least, are pretty certain to find shelter." 



The specific gravity of the roe is but little greater than 

 water; when once therefore in motion, unless intercepted, 

 it will float a considerable distance down the stream. A 

 large portion of the eggs are of course devoured; but the 

 remainder find their way into crannies, and under stones 

 inaccessible to an enemy. 



From the slow manner in which the salmon spawns, it 

 might be thought on the first view of the subject that a 



