102 INTRODUCTION. 



quantities are consumed while in the state of ova and 

 young fry, by older individuals of their own species, 

 by fish of other kinds, by wading birds and other 

 foes : whereas by a little care, the ova can be hatched 

 in perfect security, and the young fry committed to 

 the river only when they have the ability to elude 

 the pursuit of their destroyers. As illustrating this 

 subject, we shall shortly allude to the brief instruc- 

 tions on artificial breeding lately published by Sir 

 F. A. Mackenzie. On the 23d November 1840, 

 four pair of Salmon were caught, and placed in a 

 small artificial pool. A pair having commenced 

 spawning, on the following day they were carefully 

 caught, and from the female about 1200 ova were 

 gently squeezed into a basin of water, and an equal 

 quantity of milt from the male fish ; the two were 

 gently stirred and mixed, and allowed to rest for an 

 hour, when the whole was deposited and spread in 

 one of the wicker baskets recommended by Professor 

 Agassiz, having about four inches of gravel beneath 

 them, and tw-o or three above them. A similar 

 quantity of ova, treated in the same way, was also 

 deposited in one of the copper-wire bags used by 

 Mr. Shaw ; and both were then immediately placed 

 under water in the pool. In another instance the 

 ova and milt were squeezed directly into the basket 

 and copper- w^ire bag, having gravel beneath, and 

 two inches of gravel placed over them, and they too 

 were deposited in the pool. Some of the impreg- 

 nated ova were also buried in the open gravel about 

 three inches deep. On the 18th April, after 146 days, 



