NUMBER OF SALMON OVA. 65 



ing the great value of these observations, justice re- 

 quires us to record that this skilful anatomist and 

 careful observer sanctioned the mistaken idea that, in 

 three or four weeks after exclusion from the egg, the 

 young salmon assumes the silvery aspect of the smolt, 

 and migrates to the sea. For the rectification of this, 

 until lately, general belief, we are indebted not to a 

 man of science, but to Mr Shaw of Drumlanrig, forester 

 to the Duke of Buccleuch. 



The quantity of ova deposited by the salmon, though 

 by no means so great as that of many fishes, is never- 

 theless very considerable. Those of a grilse of 8 Ib. 

 amount to about 8000, while those of a salmon of 25 Ib. 

 have been found to be nearly 25,000. The period dur- 

 ing which they remain under the gravel varies with the 

 temperature of the water in which they are placed. Ova 

 deposited in September, when the temperature is high, 

 will produce fry in 90 days ; while those deposited in 

 December may remain unproductive till the 140th day. 

 In the artificial breeding-ponds of France the ova come 

 to life in 60 days, whereas in Perthshire the earliest 

 have not appeared till 120 days. A gentleman at 

 Perth, however, having deposited ova under a spring 

 flowing from a rock at Barnhill, the fry came into life, 

 some in 50, and others in 60 days. 



The ovum, on its extrusion from the salmon, is of a 

 pale-blue colour, and about the size of a small pea. It 

 is composed of a white shell and light-red yolk. On 

 the 20th day after being deposited in the gravel, a very 

 small but brilliant spot appears on one side of the yolk, 

 and this brilliancy increases daily until, on the 48th 

 day, it covers more than half the yolk, and still con- 

 tinues spreading. On the 48th day the young fish 

 make their first appearance in the form of a bluish 

 white thread in the yolk of the egg. On the 63d day 

 this formation is furnished at one end with two very 

 small black spots the eyes of the future fish. After 

 this there is a decided daily change, until the 93d 



