96 Salmon at the Antipodes. 



will hatch in about 50 days, in water at a tem- 

 perature of 50 deg. ; every degree above or 

 below this temperature shortens or lengthens 

 the time of incubation by five days. They 

 would eventually hatch out, even if the water 

 of the stream were at freezing point, but if once 

 subjected to a temperature much below 32 

 deg., it is said that their vitality is destroyed. 

 The ova of the Salmo salar, when from a 

 ripe fish in the best condition, are almost 

 exactly a quarter of an inch in diameter. 

 They are nearly globular, and of a transparent 

 pink colour. Those of the Salmo quinnat, or 

 Californian salmon, are considerably larger, 

 and are about one-third of an inch in diameter. 

 They are very easily measured in this way : 

 take a board and place it in a sloping position, 

 and lay a foot rule on its side, with the gradu- 

 ated edge on the side next the highest part of 

 the board. Place a few eggs above the rule 

 on the board and cause them to run to- 

 gether, and then count the number which lie 

 opposite three or four inches, and find the 

 average number to the inch. One lot of 

 English salmon ova that I measured were ex- 

 actly four to the inch, or a quarter of an inch in 



